Court of Appeals for the First Circuit April 15, 1981, 80-1234, 80-1235 (Transitron Electronic Corporation v. Hughes Aircraft Company, Transitron Electronic Corporation v. Hughes Aircraft Company)

LEVIN H. CAMPBELL, Circuit Judge.

This ease requires us to explore the kind of showing a patent licensee needs to make in order to recover royalties already paid under a license agreement when the patent itself is subsequently declared invalid.