Section, acts Sept. 23, 1950, ch. 1024, title I, § 3,
64 Stat. 989; Aug. 24, 1954, ch. 886, § 7(a), (b),
68 Stat. 777; May 31, 1962,
Pub. L. 87–474, § 1(a),
76 Stat. 91; Jan. 2, 1968,
Pub. L. 90–237, § 2,
81 Stat. 765, defined terms for purposes of this subchapter.