42 U.S.C. § 6211
Section, Pub. L. 94-163, title I, §102, Dec. 22, 1975, 89 Stat. 876; Pub. L. 94-385, title I, §164, Aug. 14, 1976, 90 Stat. 1142; Pub. L. 95-619, title VI, §691(b)(2), Nov. 9, 1978, 92 Stat. 3288; Pub. L. 95-620, title VIII, §802, Nov. 9, 1978, 92 Stat. 3347, provided for incentives to develop underground coal mines.