Section, Pub. L. 88–526, § 2(c), (d), Aug. 31, 1964, 78 Stat. 710, permitted the entering into of contracts for collective prospecting, development or operation of coalfields by lessees for the purpose of conserving natural resources.

Pub. L. 94–377, § 5(a), Aug. 4, 1976, 90 Stat. 1086, provided that the repeal of this section is subject to valid existing rights.