(Górecki 1992, pp. 183–185) Górecki, Piotr (1992). Economy, Society, and Lordship in Medieval Poland: 1100-1250. New York, NEW YORK: Holmes and Meier Publishers, Inc. ISBN0-8419-1318-8. OCLC25787903.
(Manteuffel 1982, p. 44) Manteuffel, Tadeusz (1982). The Formation of the Polish State: The Period of Ducal Rule, 963-1194. Detroit, MICHIGAN: Wayne State University Press. ISBN0-8143-1682-4. OCLC7730959.
