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.