Compilation, as well Mueller-Mark, "Old German States under the magnifying glass", volume 1 - 15 (5. issue), Friedemann / Wittmann "the postal stamps and cancellations of the German postal service institutes in the protectorate and abroad" Bd. 1. and 2. (4. issue) as well Kunz / stamp booklet special catalogue, Maassen / Weber ATM special handbook catalog Germany, all works in very good second-hand condition.