RADER, Circuit Judge.
In this patent infringement action, Dr. In-Bae Yoon (Yoon) and his exclusive licensee, Ethicon, Inc. (Ethicon), appeal from the judgment of the United States District Court for the District of Connecticut. In 1989, Yoon and Ethicon sued United States Surgical Corporation (U.S. Surgical) for infringement of U.S. Patent No. 4,535,773 (the ’773 patent). In 1993, the parties stipulated to the intervention of Mr. Young Jae Choi (Choi) as defendant-intervenor. Choi claimed to be an omitted co-inventor of the ’773 patent and to have granted U.S. Surgical a retroactive license under that pat[1459]*1459ent. On U.S. Surgical’s motion to correct inventorship of the ’773 patent under 35 U.S.C. § 256, the district court ruled that Choi was an omitted co-inventor of two claims, see 937 F.Supp. 1015 (D.Conn.1996), and subsequently granted U.S. Surgical’s motion to dismiss the infringement complaint, see 954 F.Supp. 51 (D.Conn.1997). Because the district court’s determination of eo-inventorship was correct, and because Choi is a joint owner of the ’773 patent who has not consented to suit against U.S. Surgical, this court affirms.
I. BACKGROUND
The ’773 patent relates to trocars, an essential tool for endoscopic surgery. A trocar is a surgical instrument which makes small incisions in the wall of a body cavity, often the abdomen, to admit endoscopic instruments. Trocars include a shaft within an outer sleeve. One end of the shaft has a sharp blade. At the outset of surgery, the surgeon uses the blade to puncture the wall and extend the trocar into the cavity. The surgeon then removes the shaft, leaving the hollow outer sleeve, through which the surgeon may insert tiny cameras and surgical instruments for the operation.
Conventional trocars, however, pose a risk of damage to internal organs or structures. As the trocar blade punctures the cavity wall, the sudden loss of resistance can cause the blade to lunge forward and injure an internal organ. The ’773 patent claims a trocar that alleviates this danger. In one embodiment, the invention equips the trocar with a blunt, spring-loaded rod. As the trocar pierces the cavity wall, the rod automatically springs forward to precede the blade and shield against injury. A second embodiment has a retractable trocar blade that springs back into a protective sheath when it passes through the cavity wall. The patent also teaches the use of an electronic sensor in the end of the blade to signal the surgeon at the moment of puncture.
Yoon is a medical doctor and inventor of numerous patented devices for endoscopic surgery. In the late 1970s, Yoon began to conceive of a safety device to prevent accidental injury during trocar incisions. Yoon also conceived of a device to alert the surgeon when the incision was complete. In 1980, Yoon met Choi, an electronics technician, who had some college training in physics, chemistry, and electrical engineering, but no college degree. Choi had worked in the research and development of electronic devices. After Choi had demonstrated to Yoon some of the devices he had developed, Yoon asked Choi to work with him on several projects, including one for safety trocars. Choi was not paid for his work.
In 1982, after collaborating for approximately eighteen months, their relationship ended. Choi believed that Yoon found his work unsatisfactory and unlikely to produce any marketable product. For these reasons, Choi withdrew from cooperation with Yoon.
In the same year, however, Yoon filed an application for a patent disclosing various embodiments of a safety trocar. Without informing Choi, Yoon named himself as the sole inventor. In 1985, the Patent and Trademark Office issued the ’773 patent to Yoon, with fifty-five claims. Yoon thereafter granted an exclusive license under this patent to Ethicon. Yoon did not inform Choi of the patent application or issuance.
In 1989, Ethicon filed suit against U.S. Surgical for infringement of claims 34 and 50 of the ’773 patent. In 1992, while this suit was still pending, U.S. Surgical became aware of Choi, and contacted him regarding his involvement in Yoon’s safety trocar project. When Choi confirmed his role in the safety trocar project, U.S. Surgical obtained from Choi a “retroactive license” to practice “Choi’s trocar related inventions.” Under the license, Choi agreed to assist U.S. Surgical in any suit regarding the ’773 patent. For its part, U.S. Surgical agreed to pay Choi contingent on its ultimate ability to continue to practice and market the invention. With the license in hand, U.S. Surgical moved to correct inventorship of the ’773 patent under 35 U.S.C. § 256, claiming that Choi was a co-inventor of claims 23, 33, 46, and 47. Following an extensive hearing, the district court granted U.S. Surgical’s motion, finding that Choi had contributed to the subject matter of claims 33 and 47.
U.S. Surgical next moved for dismissal of the infringement suit, arguing that Choi, as a joint owner of the patent, had granted it a [1460]*1460valid license under the patent. By its terms, the license purported to grant rights to use the patent extending retroactively back to its issuance. The district court granted U.S. Surgical’s motion and dismissed the suit.
Ethieon appeals the district court’s finding of co-inventorship and its dismissal of the complaint. Specifically, Ethieon contends that (1) Choi supplied insufficient corroboration for his testimony of co-invention; (2) Choi presented insufficient evidence to show co-invention of claims 33 and 47 clearly and convincingly; (3) Choi accepted illegal payment for his factual testimony which the court should therefore have excluded from the proceedings; (4) the terms of the license agreement limit it to only that part of the invention to which Choi contributed, not the entire patent; and (5) even if the agreement licenses the entire patent, it cannot release U.S. Surgical from liability for past infringement.
II. CO-INVENTORSHIP
Patent issuance creates a presumption that the named inventors are the true and only inventors. See Hess v. Advanced Cardiovascular Sys., Inc., 106 F.3d 976, 980, 41 USPQ2d 1782, 1785-86 (Fed.Cir.), cert. denied, — U.S. -, 117 S.Ct. 2459, 138 L.Ed.2d 216 (1997). Inventorship is a question of law, which this court reviews without deference. See Sewall v. Walters, 21 F.3d 411, 415, 30 USPQ2d 1356, 1358 (Fed.Cir. 1994). However, this court reviews the underlying findings of fact which uphold a district court’s inventorship détermination for clear error. See Hess, 106 F.3d at 980.
A patented invention may be the work of two or more joint inventors. See 35 U.S.C. § 116 (1994). Because “[conception is the touchstone of inventorship,” each joint inventor must generally contribute to the conception of the invention. Burroughs Wellcome Co. v. Barr Lab., Inc., 40 F.3d 1223, 1227-28, 32 USPQ2d 1915, 1919 (Fed. Cir.1994). “Conception is the ‘formation in the mind of the inventor, of a definite and permanent idea of the complete and operative invention, as it is hereafter to be applied in practice.’ ” Hybritech, Inc. v. Monoclonal Antibodies, Inc., 802 F.2d 1367, 1376, 231 USPQ 81, 87 (Fed.Cir.1986) (quoting 1 Robinson on Patents 532 (1890)). An idea is sufficiently “definite and permanent” when “only ordinary skill would be necessary to reduce the invention to practice, without extensive research or experimentation.” Burroughs Wellcome, 40 F.3d at 1228.
The conceived invention must include every feature of the subject matter claimed in the patent. See Sewall, 21 F.3d at 415. Nevertheless, for the conception of a joint invention, each of the joint inventors need not “make the same type or amount of contribution” to the invention. 35 U.S.C. § 116. Rather, each needs to perform only a part of the task which produces the invention. On the other hand, one does not qualify as a joint inventor by merely assisting the actual inventor after conception of the claimed invention. See Sewall, 21 F.3d at 416-17; Shatterproof Glass Corp. v. Libbey-Owens Ford Co., 758 F.2d 613, 624, 225 USPQ 634, 641 (Fed.Cir.1985) (“An inventor ‘may use the services, ideas and aid of others in the process of perfecting his invention without losing his right to a patent.’ ” (quoting Hobbs v. U.S. Atomic Energy Comm’n., 451 F.2d 849, 864, 171 USPQ 713, 724 (5th Cir.1971))). One who simply provides the inventor with well-known principles or explains the state of the art without ever having “a firm and definite idea” of the claimed combination as a whole does not qualify as a joint inventor. See Hess, 106 F.3d at 981 (citing O’Reilly v. Morse, 56 U.S. (15 How.) 62, 111, 14 L.Ed. 601 (1853)). Moreover, depending on the scope of a patent’s claims, one of ordinary skill in the art who simply reduced the inventor’s idea to practice is not necessarily a joint inventor, even if the specification discloses that embodiment to satisfy the best mode requirement. See Sewall, 21 F.3d at 416.
Furthermore, a co-inventor need not make a contribution to every claim of a patent. See 35 U.S.C. § 116. A contribution to one claim is enough. See SmithKline Diagnostics, Inc. v. Helena Lab. Corp., 859 F.2d 878, 888, 8 USPQ2d 1468, 1476 (Fed.Cir. 1988). Thus, the critical question for joint conception is who conceived, as that term is used in the patent law, the subject matter of the claims at issue.
[1461]*146135 U.S.C. § 256 provides that a co-inventor omitted from an issued patent may be added to the patent by a court “before which such matter is called in question.” To show eo-inventorship, however, the alleged co-inventor or co-inventors must prove their contribution to the conception of the claims by clear and convincing evidence. See Hess, 106 F.3d at 980. However, “an inventor’s testimony respecting the facts surrounding a claim of derivation or priority of invention cannot, standing alone, rise to the level of clear and convincing proof.” Price v. Symsek, 988 F.2d 1187, 1194, 26 USPQ2d 1031, 1036 (Fed.Cir.1993). The rule is the same for an alleged co-inventor’s testimony. See Hess, 106 F.3d at 980. Thus, an alleged co-inventor must supply evidence to corroborate his testimony. See Price, 988 F.2d at 1194. Whether the inventor’s testimony has been sufficiently corroborated is evaluated under a “rule of reason” analysis. Id. at 1195. Under this analysis, “[a]n evaluation of all pertinent evidence must be made so that a sound determination of the credibility of the [alleged] inventor’s story may be reached.” Id.
Corroborating evidence may take many forms. Often contemporaneous documents prepared by a putative inventor serve to corroborate an inventor’s testimony. See id. at 1195-96. Circumstantial evidence about the inventive process may also corroborate. See Knorr v. Pearson, 671 F.2d 1368, 1373, 213 USPQ 196, 200 (CCPA 1982) (“[Sufficient circumstantial evidence of an independent nature can satisfy the corroboration rule.”). Additionally, oral testimony of someone other than the alleged inventor may corroborate. See Price, 988 F.2d at 1195-96.
A. Claim 33
The district court determined that Choi contributed to the conception of the subject matter of claim 33. Claim 33 (with emphasis to highlight relevant elements) reads:
A surgical instrument for providing communication through an anatomical organ structure, comprising:
means having an abutment member and shaft longitudinally accommodatable within an outer sleeve, longitudinal movement of said shaft inside said sleeve being limited by contact of said abutment member with said sleeve, said shaft having a distal end with a distal blade surface tapering into a sharp distal point, said distal blade surface being perforated along one side by an aperture, for puncturing an anatomical organ structure when subjected to force along the longitudinal axis of said shaft;
means having a blunt distal bearing surface, slidably extending through said aperture, for reciprocating through said aperture while said abutment member is in stationary contact with said sleeve;
means positionable between said puncturing means and said reciprocating means for biasing a distal section of said reciprocating means to protrude beyond said aperture and permitting said distal section of said reciprocating means to recede into said aperture when said bearing surface is subject to force along its axis ...; and
means connectible to the proximal end of said puncturing means for responding to longitudinal movement of said reciprocating means relative to said puncturing means and creating a sensible signal having one state upon re-cision of said distal section of said reciprocating means into said aperture and another state upon protrusion of said distal section of said reciprocating means from said aperture.
To determine whether Choi made a contribution to the conception of the subject matter of claim 33, this court must determine what Choi’s contribution was and then whether that contribution’s role appears in the claimed invention. If Choi in fact contributed to the invention defined by claim 33, he is a joint inventor of that claim.
Figures 18 and 19 of the ’773 patent illustrate an embodiment of claim 33. These figures show a trocar blade with an aperture through which a blunt rod can extend. W^hen the trocar blade penetrates the inner wall of a cavity, a spring releases the rod, which juts out past the end of the trocar blade and prevents the blade from cutting [1462]*1462further. The embodiment also includes a structure that gives the surgeon aural and visual signals when the blade nears penetration.
The district court found that Yoon conceived of the use of a blunt probe. However, the court found that Choi conceived of and thereby contributed two features contained in the embodiment shown in figures 18 and 19: first, Choi conceived of locating the blunt probe in the trocar shaft and allowing it to pass through an aperture in the blade surface; second, Choi conceived of the “means ... for ... creating a sensible signal.”1
If Choi did indeed conceive of “locating the blunt probe in the shaft and allowing it to pass through an aperture in the blade surface,” he contributed to the subject matter of claim 33. Claim 33 requires that the “distal blade surface” be “perforated along one side by an aperture” and requires the “shaft” to be “longitudinally accommodatable within [the] outer sleeve.” Properly construed, claim 33 includes the elements that Choi contributed to the invention according to the district court’s findings.
In making this finding, the district court relied extensively on Choi’s testimony. Choi testified that the idea of extending the blunt probe through an aperture in the trocar blade itself was his idea. To corroborate this testimony, Choi produced a series of sketches he created while working with Yoon. One sketch shows a probe inside the shaft of a trocar blade, extending through an opening in the side of the end of the blade.
To rebut Choi’s showing, Yoon presented a drawing dated July 1973, which disclosed elements of claim 33. The district court determined, however, that Dr. Yoon had altered this drawing. In fact, according to the district court, it had originally depicted a device from an entirely different patent. Due to its suspicious origins, the trial court rejected it as unreliable.
The court also discounted Yoon’s testimony for lack of credibility. Indeed the record supports the trial court’s conclusion that Yoon altered and backdated documents to make it appear that he had independently invented trocars, shields, and electronics. Moreover, Yoon’s trial testimony clashed with his earlier deposition testimony. For instance, before learning of Choi’s role in the case, Yoon falsely testified at his deposition that (1) he had worked with Choi as early as 1975 and (2) the sketches at issue in this case had been drawn completely by him. However, the two did not meet until 1980, and when later questioned about authorship of the documents, Yoon replied, “If I said [that] at that time, then maybe I was confused.” The district court justifiably discounted Yoon’s testimony.
In sum, after full consideration of the relevant evidence, the district court determined that Choi conceived part of the invention recited in claim 33. This court detects no cause to reverse this determination.
B. Claim 47
The district court also determined that Choi contributed to the conception of the subject matter of claim 47. Claim 47 (with emphasis to highlight relevant elements) reads:
A surgical instrument for providing communication through an anatomical organ structure, comprising:
means having an elongate shaft exhibiting a longitudinal axis and terminating in a sharp, distal end, for puncturing the cavity wall of an anatomical organ structure;
means borne by said puncturing means distal end for converting counterforce exerted by said cavity wall against said distal end into transmissible energy;
means connected to said converting means for conveying said transmissible energy toward the proximal end of said puncturing means;
[1463]*1463means having an interior bore coaxially aligned with the longitudinal axis of said shaft for receiving said puncturing means proximal end;
means for biasing said puncturing means proximal end to withdraw into said interior bore;
means interposed between said puncturing means proximal end and said interior bore assuming a normally protruding position for determining [sic: detaining
2
] said puncturing means proximal end extended from said interior cavity in opposition to said biasing means.
To determine whether Choi made a contribution to the conception of the subject matter of claim 47, this court must determine what Choi’s contribution was and then construe the claim language to determine if Choi’s contribution found its way into the defined invention.
Figures 34, 35, and 36 illustrate the invention in claim 47. In these embodiments, a cocked spring pulls the trocar back into a protective sheath as soon as the blade has punctured the inner wall. Release of the detaining means triggers the retracting spring action. The two detaining means disclosed in the specification are (1) a detent3 extending radially outward from the trocar through a hole in the sheath and (2) a rod extending horizontally from the proximal end of the trocar that butts against an off-center, but slidable, bar with a hole in its center. In the ease of the detent detaining means, when a sensor detects that the trocar blade has pierced the wall of a cavity, the plunger of a solenoid pushes the detent out of the hole in the sheath. In the ease of the rod detaining means, the solenoid plunger positions the bar so that the hole in its center aligns with the rod.
The district court concluded that Yoon generally invented the retractable trocar, but that Choi invented both of the detaining means disclosed in the specification. In addition to oral testimony of the parties, the district court cited Choi’s sketches, one of which clearly shows the rod detaining means. However, the sketch in which the district court would find the detent detaining means appears to work differently than the embodiment described in the ’773 patent. Instead of a detent that extends radially outward through a hole in the sheath, the sketch illustrates the use of the solenoid plunger itself as a detent, extending radially inward through a hole in the sheath. Thus, the record does not show that Choi contributed to the detent detaining means. Therefore, this court affirms the district court’s finding that Choi contributed the rod detaining means, but determines that the trial court clearly erred in finding that Choi contributed the detent detaining means.
In this instance, however, claim 47 recites a “means ... for [detaining].” The use of the word “means” gives rise to “a presumption that the inventor used the term advisedly to invoke the statutory mandates for means-plus-funetion clauses.” York Prods., Inc. v. Central Tractor Farm & Family Ctr., 99 F.3d 1568, 1574, 40 USPQ2d 1619, 1623 (Fed.Cir.1996). Although the presumption is not conclusive, see, e.g., id. (construing “means” in claim without reference to section 112, paragraph 6), the means language here invokes the interpretation regimens of section 112, paragraph 6. Thus applying section 112, paragraph 6 to interpret this claim, the language adopted the two structures in the specification to define the means for detaining.
Choi showed contribution to one of these alternative structures. The contributor of any disclosed means of a means-plus-function claim element is a joint inventor as to that claim, unless one asserting sole inventorship can show that the contribution of that means was simply a reduction to practice of the sole inventor’s broader concept. See Se-wall, 21 F.3d at 416 (holding that the design[1464]*1464er of one disclosed means was not a joint inventor). Although the district court found that Yoon first conceived of a retractable trocar generally, Yoon did not show that Choi’s contribution was simply a reduction to practice of the broader concept of using any detaining means commensurate with the scope of claim 47. Thus, Choi showed entitlement to the status of co-inventor for this claim as well.
C. Corroboration
As corroboration for his testimony of co-invention, Choi proffers sketches of his work. These sketches were in Yoon’s possession since their creation. The parties do not dispute, however, that Choi in fact created the sketches. Instead, Yoon contends that he first disclosed the invention to Choi, who then made the sketches to illustrate what he learned from Yoon. Absent sufficient corroboration, inventorship would turn solely on a credibility contest between Yoon and Choi. The district court, however, found sufficient corroboration.
Taken together, the alleged co-inventor’s testimony and the corroborating evidence must show inventorship “by clear and convincing evidence.” This requirement is not to be taken lightly. Under the “rule of reason” standard for corroborating evidence, Holmwood v. Sugavanam, 948 F.2d 1236, 1238-39, 20 USPQ2d 1712, 1714 (Fed.Cir. 1991), the trial court must consider corroborating evidence in context, make necessary credibility determinations, and assign appropriate probative weight to the evidence to determine whether clear and convincing evidence supports a claim of eo-inventorship.
Accordingly, there need not be corroboration for every factual issue contested by the parties. For example, in Price, the junior party in an interference proceeding proffered drawings of his conceived invention, his affidavit that he had conceived the invention before the critical date, and an affidavit from a third person stating that she had seen one of the drawings before that time. However, the junior party lacked corroborating evidence that it was he who had created the drawings because the third party could not attribute the drawings to him. This court held that “all of the evidence put forth” should have been considered and acknowledged that “an inventor can conceivably prove prior conception by clear and convincing evidence although no one piece of evidence in and of itself establishes the prior conception.” Price, 988 F.2d at 1196.
In this case, Choi’s sketches show the invention. The parties agree that Choi made the sketches. The contest involves whether Choi conceived of the material in the sketches or merely drew what Yoon conceived. The district count noted many circumstantial factors further corroborating Choi’s conception claim: (1) Yoon’s need for a person with expertise in electronics; (2) Choi’s background in electronics, (3) Yoon’s proposal that he and Choi should work together to develop new products, including safety trocars, (4) their informal business relationship, (5) the length of time they worked together, (6) the absence of any pay to Choi for his work, (7) the similarity between Choi’s sketches and the patent figures, and (8) the letter in which Choi stated that he could no longer be a “member” of Yoon’s business. Additionally, U.S. Surgical introduced expert testimony that some of the sketches dealt with sophisticated concepts that only an electrical engineer or technician would understand. Consequently, the district court found that Choi was presenting ideas to Yoon as the sketches were drawn, rather than the other way around.
On appeal, this court declines to reweigh the evidence. Instead, this court determines that the record shows that corroboration evidence in this case satisfies the “rule of reason.” Thus, this court must only further assess whether the district court’s factual conclusions, given the clear and convincing evidence standard, were clearly erroneous. Here, given the sketches, Choi’s testimony, and the established circumstances, in contrast with Yoon’s testimony, expressly found to lack credibility by the trial court, this court discerns no clear error.
In reaching this determination, this court has also considered alleged inconsistencies in Choi’s testimony. In August 1992, U.S. Surgical’s counsel first sent Choi a copy of the ’773 patent. Choi circled figures and claims describing that which he claimed to have contributed. Choi circled some claims [1465]*1465that he does not now assert to have had a role in inventing. He also did not circle claims he now claims to have co-invented. However, the district court could have reasonably found that a layman, untrained in the language of the patent law, may reasonably err in interpreting claim language. Moreover, Choi might well have confused the legal distinction between conception (which justifies a finding of inventorship) and reduction to practice (which does not). In any event, this court affirms the district court’s holding that Choi was a co-inventor of claims 33 and 47.4
III. ADMISSIBILITY ISSUES
Under the terms of its license agreement, U.S. Surgical gave Choi an immediate payment of $300,000. Future payments of up to $100,000 per year for ten years are contingent on U.S. Surgical’s prevailing in this action. In return, Choi granted U.S. Surgical an exclusive license in “Choi’s trocar related inventions.” In addition, Choi agreed to testify in a proceeding to correct inventor-ship of the ’773 patent and to “render all reasonable assistance requested by [U.S. Surgical] to defend or settle” this action. As the district court concluded, these license agreement terms do not constitute payment for testimony as a fact witness.
This court reviews matters pertaining to the admissibility of evidence under the law of the particular regional circuit where appeals from the district court would normally he. The Second Circuit accords trial courts broad discretion to determine the admissibility of evidence. See Perry v. Ethan Allen, Inc., 115 F.3d 143, 150 (2d Cir.1997). To warrant appellate correction, a trial court must commit an abuse of that broad discretion. See id.
A patent license agreement that binds the inventor to participate in subsequent litigation is very common. Indeed, Yoon’s agreement with Ethieon contains a similar clause. This sort of agreement simply assures the licensee that it will be able to defend the property in which it has purchased an interest.
Furthermore, a witness’s pecuniary interest in the outcome of a case goes to the probative weight of testimony, not its admissibility. See, e.g., Den Norske Bank AS v. First Nat’l Bank of Boston, 75 F.3d 49, 58 (1st Cir.1996) (holding that interests of expert witnesses who were employees of plaintiff affected the weight of their testimony, not its admissibility). The district court did not abuse its discretion by admitting Choi’s testimony into evidence, subject to cross-examination that might expose Choi’s bias.
IV. SCOPE OF THE CHOI-U.S. SURGICAL LICENSE
Questions of patent ownership are distinct from questions of inventorship. See Beech Aircraft Corp. v. EDO Corp., 990 F.2d 1237, 1248, 26 USPQ2d 1572, 1582 (Fed.Cir.1993). In accordance with this principle, this court has nonetheless noted that “an invention presumptively belongs to its creator.” Teets v. Chromalloy Gas Turbine Corp., 83 F.3d 403, 406, 38 USPQ2d 1695, 1697 (Fed.Cir.), cert. denied, — U.S. -, 117 S.Ct. 513, 136 L.Ed.2d 402 (1996).
Indeed, in the context of joint inventorship, each co-inventor presumptively5 owns a pro rata undivided interest in the entire patent, no matter what their respective contributions. Several provisions of the Patent Act combine to dictate this rule. 35 U.S.C. § 116, as amended in 1984,6 states that a joint inventor need not make a contribution “to the subject matter of every claim of the patent.” In amending section 116 as to joint inventorship, Congress did not make corresponding modifications as to joint ownership. For example, section 261 continues to provide that “patents shall have the attrib[1466]*1466utes of personal property.” This provision suggests that property rights, including ownership, attach to patents as a whole, not individual claims. Moreover, section 262 continues to speak of “joint owners of a patent,” not joint owners of a claim. Thus, a joint inventor as to even one claim enjoys a presumption of ownership in the entire patent.
This rule presents the prospect that a co-inventor of only one claim might gain entitlement to ownership of a patent with dozens of claims. As noted, the Patent Act accounts for that occurrence: “Inventors may apply for a patent jointly even though ... each did not make a contribution to the subject matter of every claim.” 35 U.S.C. § 116 (emphasis added). Thus, where inventors choose to cooperate in the inventive process, their joint inventions may become joint property without some express agreement to the contrary. In this case, Yoon must now effectively share with Choi ownership of all the claims, even those which he invented by himself. Thus, Choi had the power to license rights in the entire patent.
This court next examines the extent to which Choi exercised that power. This court reviews the interpretation of contractual language, including license agreements, as a question of law. See Intel Corp. v. ULSI Sys. Tech., Inc., 995 F.2d 1566, 1569, 27 USPQ2d 1136, 1138 (Fed.Cir.1993). State law, in this case Connecticut law, controls in matters of contract interpretation. Thus, in making its review, this court adopts the ordinary and common meaning of contract terms whenever possible. See Sturman v. Socha, 191 Conn. 1, 463 A.2d 527, 532 (1983).
The license which Choi granted to U.S. Surgical states:
Choi hereby grants to U.S. Surgical an exclusive, worldwide right and license to make, have made, use, market and sell Choi’s trocar related inventions, including trocars having shields and those described and/or claimed in the ’773 patent. This license is retroactive to the date on which the ’773 patent issued.
U.S. Surgical reads this language to cover all trocars “described and/or claimed in the ’773 patent,” encompassing the entire ’773 patent and more. Ethicon reads the same language as limited to “Choi’s trocar related inventions,” which comprise only his contributions to claims 33 and 47 of the ’773 patent.
The meaning of the phrase “including tro-cars ... described and/or claimed in the ’773 patent” depends on the meaning of the word “including.” If construed to merely clarify the meaning of “trocar related inventions,” the phrase it modifies, then “including” could limit the scope of Choi’s grant. “Including,” however, can also operate as a phrase of addition. Under this broader reading, the phrase “trocar related inventions” covers more than just the material specified in the “including” phrase.
If possible, this court must view a single provision of a contract in the way that gives meaning to — and provides internal harmony among — all parts of the contract. See Barnard v. Barnard, 214 Conn. 99, 570 A.2d 690, 696 (1990). Read in context, the “including” phrase is a phrase of addition, not a limitation on the scope of “trocar related inventions.” For example, the agreement states that Choi “has not ... and shall not, grant to any other person ... any right or license to make, use or sell any of his trocar related inventions or any device described or within the scope of any of the claims of the ’773 patent.” (emphasis added). In addition, the agreement states, “Choi hereby grants to [U.S. Surgical] the sole right to sue any infringer of the ’773 patent....” If the scope of the license did not encompass all of Choi’s rights as a joint owner of the ’773 patent, these supplementary provisions were inexplicably much too broad. Rather, in context, Choi’s grant meant to license all of his rights as a joint owner under the ’773 patent.
Thus, the district court’s interpretation of the Choi license was correct as a matter of law.
V. RETROACTIVE LICENSURE
Finally, Ethicon argues that even if the license agreement is enforceable as to the entire patent, it should still be allowed to proceed against U.S. Surgical to recover damages for pre-license infringement. Ethicon contends that to hold otherwise would contravene the decision in Schering Corp. v. [1467]*1467Roussel-UCLAF SA, 104 F.3d 341, 41 USPQ2d 1359 (Fed.Cir.1997). This court agrees with Ethieon’s challenge to the retroactive effect of Choi’s license, but must affirm the dismissal of the case based on Choi’s refusal to join as plaintiff in the suit.
In Schering, Roussel and Schering, the two co-owners of the patent in suit, entered into an agreement whereby each granted the other a unilateral right to sue third parties for infringement. Schering then sued to enjoin Zeneca, Inc. from proceeding with planned sales of an allegedly infringing product. Schering joined Roussel in the action as an involuntary plaintiff. Two weeks later, Roussel granted Zeneca a license to practice the patented invention. The district court dismissed Schering’s suit. Schering appealed.
On appeal, Schering argued that because Roussel had granted Schering a unilateral right to sue, Roussel could not now grant a license to Zeneca. Schering contended that one grant was incompatible with the other. The court rejected Shering’s argument, reasoning that “[t]he right to license and the unilateral right to sue are ... not incompatible, and the granting of one does not necessarily imply the relinquishment of the other.” Id. at 345. This court acknowledged the critical distinction that a license to a third party only operates prospectively. Absent agreement to the contrary, a co-owner cannot grant a release of another co-owner’s right to accrued damages. Consequently, a co-owner who has granted a unilateral right to sue to another co-owner may also license a third party. Nevertheless, by virtue of the unilateral right to sue, the second co-owner can still force the first co-owner to join an infringement action against the licensee to recover the second co-owner’s accrued damages for past infringement. Thus, a prospective license is not per se incompatible with a unilateral right to sue, and, barring any other applicable contractual provision, Schering could not prevent Roussel from granting a license to Zeneca:7
[T]he grant of a license by one co-owner cannot deprive the other co-owner of the right to sue for accrued damages for past infringement. That would require a release, not a license, and the rights of a patent co-owner, absent agreement to the contrary, do not extend to granting a release that would defeat an action by other co-owners to recover damages for past infringement.
Id. at 345.
Thus, Choi’s “retroactive license” to U.S. Surgical attempts to operate as the combination of a release and a prospective license.8 Nonetheless Choi cannot release U.S. Surgical from its liability for past accrued damages to Ethicon, only from liability to himself.
One more settled principle governs this case, however. An action for infringement must join as plaintiffs all co-owners. See Waterman v. Mackenzie, 138 U.S. 252, 255, 11 S.Ct. 334, 335, 34 L.Ed. 923 (1891) (“The patentee or his assigns may, by instrument in writing, assign, grant, and convey, either (1) the whole patent ...; or (2) an undivided part or share of that exclusive right; or (3) the exclusive right under the patent within and throughout a specified part of the United States. A transfer of either of these three kinds of interests is an assignment, properly speaking, and vests in the assignee a title in so much of the patent itself, with a right to sue infringers. In the second case, jointly with the assignor. In the first and third cases, in the name of the assignee alone.” (emphasis added)); Moore v. Marsh, 74 U.S. (7 Wall.) 515, 520, 19 L.Ed. 37 (1868) (“[W]here [an] assignment is of an undivided part, of the patent, the action [1468]*1468should be brought for every infringement committed subsequent to the assignment, in the joint names of the patentee and assignee, as representing the entire interest.”).
Further, as a matter of substantive patent law, all eo-owners must ordinarily consent to join as plaintiffs in an infringement suit.9 Consequently, “one co-owner has the right to impede the other co-owner’s ability to sue infringers by refusing to voluntarily join in such a suit.” Schering, 104 F.3d at 345.
This rule finds support in section 262 of the Patent Act:
In the absence of any agreement to the contrary, each of the joint owners of a patent may make, use, offer to sell, or sell the patented invention within the United States, or import the patented invention into the United States, without the consent of and without accounting to the other owners.
This freedom to exploit the patent without a duty to account to other co-owners also allows co-owners to freely license others to exploit the patent without the consent of other co-owners. Schering, 104 F.3d at 344 (“Each co-owner’s ownership rights carry with them the right to license others, a right that also does not require the consent of any other co-owner.”). Thus, the congressional policy expressed by section 262 is that patent co-owners are “at the mercy of each other.” Willingham v. Lawton, 555 F.2d 1340, 1344, 194 USPQ 249, 252 (6th Cir.1977).
Although in this case, the result is effectively no different than if Choi could grant a release to U.S. Surgical of any liability to Ethicon, it should be emphasized that the principle that governs this case is not incompatible with the principle enunciated in Schering. In Schering, this court noted that the granting of a unilateral right to sue is not incompatible with the right to grant a license. Similarly, this court notes that the inability to grant a release is not incompatible with the right to refuse to consent to an infringement suit. It is true that, in some circumstances, the decision of one co-owner to not join an infringement suit may have the same effect as granting a release, but this is not true in all cases. For example, when co-owners have granted each other a unilateral right to sue, each has waived his right not to join an infringement suit, and either of them can force the other to join a suit to collect accrued infringement damages.
Because Choi did not consent to an infringement suit against U.S. Surgical and indeed can no longer consent due to his grant of an exclusive license with its accompanying “right to sue,” Ethieon’s complaint lacks the participation of a co-owner of the patent. Accordingly, this court must order dismissal of this suit.
VI. CONCLUSION
Accordingly, the judgment of the United States District Court for the District of Connecticut is affirmed.
COSTS
Each party shall bear its own costs.
AFFIRMED.