Wikimedia Commons by Tentotwo Zahlen aus: Eltjo Buringh; Jan Luiten van Zanden: „Charting the “Rise of the West”: Manuscripts and Printed Books in Europe, A Long-Term Perspective from the Sixth through Eighteenth Centuries“, in: The Journal of Economic History, Bd. 69, Nr. 2 (2009), S. 409–445 (416–417, Tafeln 1&2)