Arthur William Holland, 1911 Encyclopædia Britannica, Volume 13… (1911)
“ The subsequent history of this branch of the Hohenzollerns is identified with that of Brandenburg from 1415 to 1701, and with that of Prussia since the latter date, as in this year the elector Frederick III. became king of Prussia. In 1871 William, the seventh king, took the title of German emperor. While the electorate of Brandenburg passed according to the rule of primogeniture, the Franconian possessions of the Hohenzollerns, Ansbach and Bayreuth, were given as appanages to younger sons, an arrangement which was confirmed by the dispositio Achillea of 1473. ”
