Section 5(a) of the Act of July 15, 1968, 82 Stat. 354, 16 U.S.C. 4601-22(a), authorizes the Secretary of the Interior, under specified conditions, to convey a leasehold or freehold interest on federally owned real property acquired by the Secretary from non-Federal sources within any unit of the National Park System except national parks and those national monuments of scientific significance. This legislation is referred to as ``the act'' in regulations in this part.