Eduard Fueter (1922)۔ World history, 1815–1930۔ United States of America: Harcourt, Brace and Company۔ صفحہ: 25–28, 36–44۔ ISBN1-58477-077-5۔ Great Powers Congress of Vienna.
ia800202.us.archive.org
Henry Davis: Medieval Europe. Williams and Norgate, London 1911, p. 55: "These crowded years of war leave the Frankish Empire established as the one great power west of the Elbe and Adriatic."
ios-regensburg.de
hgsoe.ios-regensburg.de
Daniel Ziemann: Das Erste bulgarische Reich. Eine frühmittelalterliche Großmacht zwischen Byzanz und Abendland. (German: An early medieval great power between Byzantium and the Occident) In: Online handbook on the history of South-East Europe. Volume I Rule and politics in Southeastern Europe until 1800. Published by the Institute for East and Southeast European Studies of the Leibniz Association, Regensburg 2016
