U.S. Department of the Interior, U.S. Geological Survey, National Mapping Division, Digital Gazeteer: Users Manual, (Reston, Virginia: U.S. Geological Survey, 1994).
2014년 1월 11일에 보존된 문서.  U.S. Department of the Interior, U.S. Geological Survey, National Mapping Division, Digital Gazeteer: Users Manual, (Reston, Virginia: U.S. Geological Survey, 1994).