Sections 5101, 5108, 5110, 5111, 5121, 5124, and 5129 of this title shall after May 1, 1936, apply to the Territory of Alaska: Provided, That groups of Indians in Alaska not recognized prior to May 1, 1936, as bands or tribes, but having a common bond of occupation, or association, or residence within a well-defined neighborhood, community, or rural district, may organize to adopt constitutions and bylaws and to receive charters of incorporation and Federal loans under sections 5113, 5123, and 5124 of this title.