(页面存档备份,存于互联网档案馆) International Max Planck Research School for Computer Science (页面存档备份,存于互联网档案馆) University of Darmstadt (页面存档备份,存于互联网档案馆) VLDB Endowment (页面存档备份,存于互联网档案馆)
World (c.751–877) (Leiden: Brill, 2008). Egon Boshof: Ludwig der Fromme. Darmstadt 1996, p. 89 The Making of Charlemagne's Europe (768-814)(页面存档备份,存于互联网档案馆)