Area data were initially assembled in either square kilometers or square miles and converted from one to the other on the basis of the factors .3861 (from K2 to M2) and 2.590 (from M2 to K2). As in a limited number of other original data fields, where an unusually large number of individual sources were consulted, no bibliographic references are provided for most of the area data. A substantial portion of the latter for the earlier years were, however, derived from the Almanach de Gotha, the Journal of the Royal Statistical Society (London), and The Statesman's Yearbook.