Section 16.1 - Definitions(a) The term Secretary means the Secretary of the Interior and his authorized representatives.(b) The term Bureau means the Bureau of Indian Affairs, acting through the Commissioner of Indian Affairs and his authorized representatives, including field officials who are responsible for matters affecting properties in which a restricted interest is owned by an Indian of the Five Civilized Tribes.(c) The term Field Solicitor means the Regional Solicitor, Southwest Region, Page Belcher Federal Building, P.O. Box 3156, Tulsa, Oklahoma 74101.(d) The term Indian of the Five Civilized Tribes means an individual who is either an enrolled member of the Cherokee, Chickasaw, Choctaw, Creek, or Seminole Tribes of Oklahoma, or a descendant of an enrolled member thereof.(e) The term restricted interest means an interest owned in real or personal property subject to restraints upon alienation imposed either by Federal statute or by administrative action authorized by Federal statute. Although this term includes property subject to restraints which may be removed by administrative action, its use in this part refers primarily to property subject to restraints which State courts have jurisdiction to remove in proceedings such as those specified in § 16.2 .37 FR 7082, Apr. 8, 1972, as amended at 50 FR 12529, Mar. 29, 1985