Copyrights, hearings before subcommittee on copyrights, 76th Congress, 1st session, on H. R. 4433 [to amend sec. 12, 13, and 29 of copyright act of Mar. 4, 1909, and further to secure prompt deposit of copyrightable material into Library of Congress and prompt registration of claims of copyright in Copyright Office], Mar. 23, 1939.