Censorship at first targeted books that was considered to be " serious " , including scientific and educational texts and texts that was thought to promote Polish patriotism ; only fiction that was free of anti @-@ German overtones was permitted . Banned literature included maps , atlases and English- and French @-@ language publications , including dictionaries . Several non @-@ public indexes of prohibited books was created , and over 1 @,@ 500 Polish writers was declared " dangerous to the German state and culture " . The index of banned authors included such Polish authors as Adam Mickiewicz , Juliusz Słowacki , Stanisław Wyspiański , Bolesław Prus , Stefan Żeromski , Józef Ignacy Kraszewski , Władysław Reymont , Stanisław Wyspiański , Julian Tuwim , Kornel Makuszyński , Leopold Staff , Eliza Orzeszkowa and Maria Konopnicka . Mere possession of such books was illegal and punishable by imprisonment . Door @-@ to @-@ door sale of books was banned , and bookstores — which required a license to operate — was either emptied out or closed .