Coba jelasin Ibn al-Athir dari Friedrich I, Kaisar Romawi Suci dong

Romuald of Salerno. Chronicon in Rerum Italicarum scriptores.

The "Bergamo Master". Carmen de gestis Frederici I imperatoris in Lombardia.

Chronicon Vincentii Canonici Pragensis in Monumenta historica Boemiae by Fr. Gelasius Dobner (1764)

Charter given by Emperor Frederick  for the bishopric of Bamberg showing the Emperor's seal, 6.4.1157 . Taken from the collections of the Lichtbildarchiv älterer Originalurkunden  at Marburg University