In Warner-Lambert Pharm. Co. v. John J. Reynolds, Inc. (S.D.N.Y. 1959) 178 F.Supp. 655, the federal district court was asked to decide whether the defendants were required to make periodic payments for its manufactured and sale of Listerine. (Id. at p. 657.) The court found the language of the parties' agreement to unambiguously require payments as long as the defendants manufacture and sold Listerine. (Id. at p. 660.) The court also found the conduct of the parties over the term of the contract to be persuasive of the intent of the parties. (Id. at p. 667.)