Althoff, Gerd (2003). Otto III(PDF). Published by The Pennsylvania State University Press. pp. 124–125. ISBN0271022329. Archived(PDF) from the original on 9 October 2022. Retrieved 20 July 2022.
ghostarchive.org
Althoff, Gerd (2003). Otto III(PDF). Published by The Pennsylvania State University Press. pp. 124–125. ISBN0271022329. Archived(PDF) from the original on 9 October 2022. Retrieved 20 July 2022.
treccani.it
Longhena et al. 1935. Longhena, Mario; Levi Spinazzola, Alda; Pettorelli, Arturo; Parigi, Luigi; De Marinis, Tammaro; Carotti, Natale (1935). "Piacenza". Enciclopedia Italiana. Rome: Istituto dell'Enciclopedia Italiana.