Lyndon Johnson actually said...
By virtue of the authority vested in me by section 55(a) of the Internal Revenue Code of 1939, as amended (53 Stat. 29, 54 Stat. 1008; 26 U.S.C. (1952 Ed.) 55(a)), and by section 6103(a) of the Internal Revenue Code of 1954, as amended (68A Stat. 753; 26 U.S.C. 6103(a)), it is hereby ordered that any income, excess-profits, estate, or gift tax return for the years 1947 to 1965, inclusive, shall, during the Eighty-ninth Congress, be open to inspection by the Committee on Un-American Activities, House of Representatives, or any duly authorized subcommittee thereof, for the purpose of carrying on those investigations of subversive and un-American activities and propaganda authorized by clause 18 of Rule XI of the Rules of the House of Representatives, agreed to January 4, 1965.
04/23/1965