Because Congress did not define procedures for readjusting leases, regulations setting forth those procedures are within the Secretary's authority so long as the regulations are not contrary to the Act of 1920, as amended. See Ramoco Inc. v. Andrus, 649 F.2d 814, 816 (10th Cir. 1981). The purposes of the Federal Coal Leasing Amendments Act was "to provide a more orderly procedure for the leasing and development of coal presently owned by the United States and to assure its development in a manner compatible with the public interest."