Erwin Assmann: Friedrich Barbarossas Kinder (页面存档备份,存于互联网档案馆) In: German Archives for Research into the Middle Ages, Vol. 33 (1977), pp. 435–472, footnote p. 459.
Erwin Assmann: Friedrich Barbarossas Kinder (页面存档备份,存于互联网档案馆) In: German Archives for Research into the Middle Ages, Vol. 33 (1977), pp. 435–472, footnote p. 459.