As used in this chapter mineral leasing laws shall mean the Act of October 20, 1914 (38 Stat. 741); the Act of February 25, 1920 (41 Stat. 437) [
30 U.S.C.
181 et seq.]; the Act of April 17, 1926 (44 Stat. 301) [
30 U.S.C.
271 et seq.]; the Act of February 7, 1927 (44 Stat. 1057) [
30 U.S.C.
281 et seq.] and all Acts heretofore or hereafter enacted which are amendatory of or supplementary to any of the foregoing Acts.