Grupa, M., M. Krajewska, M. Majorek, and T. Kozłowski. “The Influence of Trade Contacts on Grave Equipment of Gniew Community in the 14th-18th Century”. Geology, Geophysics and Environment, vol. 39, no. 2, June 2013, p. 133, doi:10.7494/geol.2013.39.2.133.