The Polish press in the Ruhr district and the leading role of Wiarus Polski, 1891-1923 - Murzynowska, Krystyna; Kleßmann, Christoph; Winter, Andrew (. The @press of labor migrants in Europe and North America 1880s to 1930s. - Bremen : Univ., Druckschriftenlager, 1985. - 602 S.. - Ill.. - ISBN 3-88722-115-X, 1985)