Sources
- Robinson, I. S. (2003) [1999]. Henry IV of Germany, 1056-1106. Cambridge University Press. ISBN 0-521-54590-0.
- Eldevik, John (2012). Episcopal Power and Ecclesiastical Reform in the German Empire: Tithes, Lordship, and Community, 950–1150. Cambridge University Press. ISBN 978-0-521-19346-7.
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