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"Complete Files of Geographic Names for Geopolitical Areas from GNS". Toponymic information is based on the Geographic Names Database, containing official standard names approved by the United States Board on Geographic Names and maintained by the National Geospatial-Intelligence Agency. More information is available at the Maps and Geodata link at http://www.nga.mil. The National Geospatial-Intelligence Agency name, initials, and seal are protected by 10 United States Code Section 425. Retrieved 2013-02-20.
National Geospatial-Intelligence Agency. "GeoNames WMS Viewer". Retrieved 2013-02-20.