The country codes are two- or three-character lowercase alphabetic strings.  National entities are generally assigned a two-character code (exceptions are noted below).  When possible, the first letter of the code is the same as the first letter of the place name in most cases.  When there were insufficient available codes beginning with the first letter of the place name to accommodate all of the place names that begin with that letter of the alphabet, a code with x as the first letter was assigned, e.g., Marshall Islands (xe).

Three-character codes are assigned to states of the United States, provinces and territories of Canada and divisions of the United Kingdom.  In this case, the first two characters represent the constituent part, and the third character represents the country, e.g., nyu for New York.  Three-character codes are also used for the United States (xxu), Canada (xxc), and the United Kingdom (xxk) when the state, province or territory, or division is not known, but the country is known, or when it is not desired to code at the lower level.  In this case, the first two characters (xx) represent "unknown or undetermined," and the third character represents the country.

Codes are assigned according to present geographic boundaries.  A place which has historically been located in more than one political jurisdiction is coded for the jurisdiction in which it is presently located.

When a place is given in the bibliographic record with a question mark, a corresponding country code is assigned without regard to the uncertainty.  If the place is completely unknown, or undetermined, the code xx is used (see Special Codes for Special Situations).

See also:

Introduction