 <unk> at first targeted books that were considered to be " serious " , including scientific and educational texts and texts that were thought to promote Polish patriotism ; only fiction that was free of anti @-@ German overtones was permitted . <unk> literature included maps , <unk> and <unk> and French @-@ language publications , including dictionaries . Several non @-@ public <unk> of prohibited books were created , and over 1 @,@ 500 Polish writers were declared " dangerous to the German state and culture " . The index of banned authors included such Polish authors as Adam Mickiewicz , Juliusz <unk> , Stanisław <unk> , Bolesław <unk> , Stefan <unk> , <unk> <unk> <unk> , Władysław <unk> , Stanisław <unk> , Julian <unk> , <unk> <unk> , Leopold Staff , Eliza <unk> and Maria <unk> . Mere possession of such books was illegal and punishable by imprisonment . <unk> @-@ to @-@ door sale of books was banned , and <unk> — which required a license to operate — were either emptied out or closed . 
