Friedemann / Wittmann, the postal stamps and cancellations of the German postal service institutes in the protectorate and abroad, 1988, Hdb. And special -catalogue, 4. Last edition in 2 volumes, 865 S., many illustration, long-standing out of print and not again put on, good used condition

Gibbs, R. M., G. R. I. - The Postage Stamps of the German Colonies Occupied by the britisch 1914-1918, 1987, the standard work for the GRI overprints, contains a detailed cataloging of the stamps and postal stationery with plate flaws, varieties and so on and besides background information, the cancel, with rarity information, numerous illustrations, partly also coloured, 275 sides, linen letter with dust cover.

J+ñschke Lantelme, the handstamp overprints from Tientsien, German post offices in China, Michel number 8-14 and I-IV, 2004, Monograph, with to scold to the origin and use of the issue, cancel, forgeries and so on, 116 sides, with illustrations, partly coloured, valuations, cover slightly bumped.