GEOPOLITICAL ENTITIES, NAMES, and CODES (GENC): The Geopolitical Entities, Names, and Codes (GENC) Standard Edition 3.0.1 (2016) is the US Government-approved profile of names of countries and country subdivisions. Originally based on ISO 3166 (see below), it specifies an authoritative set of country codes and names for use by the US Federal Government for information exchange.

ISO 3166: Codes for the Representation of Names of Countries (ISO 3166) is prepared by the International Organization for Standardization. ISO 3166 includes two- and three-character alphabetic codes and three-digit numeric codes that may be needed for activities involving exchange of data with international organizations that have adopted that standard.

STANAG 1059: Letter Codes for Geographical Entities (8th edition, 2004) is a Standardization Agreement (STANAG) established and maintained by the North Atlantic Treaty Organization (NATO/OTAN) for the purpose of providing a common set of geo-spatial identifiers for countries, territories, and possessions. The 8th edition established trigraph codes for each country based upon the ISO 3166-1 alpha-3 character sets.

Internet: The Internet country code is the two-letter digraph maintained by the International Organization for Standardization (ISO) in the ISO 3166 Alpha-2 list and used by the Internet Assigned Numbers Authority (IANA) to establish country-coded top-level domains (ccTLDs).