Contributory infringement in patents; Definition of invention : hearings before Subcommittee on Patents, Trade-marks, and Copyrights of the Committee on the Judiciary, House of Representatives, Eightieth Congress, second session on H.R. 5988, a bill to provide for the protection of patent rights where enforcement against direct infringements is impracticable, to define "contributory infringement," and for other purposes : H.R. 4061, a bill to establish a criterion of invention with respect to patent applications and issued patents and to amend Section 4886 of the Revised statutes and for other purposes : H.R. 5248, a bill to declare the national policy regarding the test for determining invention, May 5, 7, and 12, 1948.