30 U.S.C. § 121: Agricultural entry or purchase of lands withdrawn or classified as containing phosphate, nitrate, potash, oil, or gas; reservations to United States; application

Lands withdrawn or classified as phosphate, nitrate, potash, oil, gas, or asphaltic minerals, or which are valuable for those deposits, shall be subject to appropriation, location, selection, entry, or purchase, if otherwise available, under the nonmineral land laws of the United States, whenever such location, selection, entry, or purchase shall be made with a view of obtaining or passing title with a reservation to the United States of the deposits on account of which the lands were withdrawn or classified or reported as valuable, together with the right to prospect for, mine, and remove the same. All applications to locate, select, enter, or purchase under this section shall state that the same are made in accordance with and subject to the provisions and reservations of sections 121 to 123 of this title.