Literature About German Stamp Essays, Proofs

Hi,

Is there exist any books, catalogues (literature), about german stamp essays proofs plate flaws?(in english or german language)
If yes ,can you tell me where can I find them?

Thanks.

Any particular period?

German states, ddr, west berlin.

OK. Here are a few plate flaw catalogs.

German States
Philotax Altdeutschland Plattenfehler-Katalog (Philotax German States Plate Flaw Catalog)

DDR
Michel Plattenfehler DDR, 1949-1969 (Michel Plate Flaw Catalog, DDR 1949-1969)
Michel Plattenfehler DDR, 1970-1990 (Michel Plate Flaw Catalog, DDR 1970-1990)
Philotax DDR Plattenfehler-Katalog (Philotax DDR Plate Flaw Catalog)
Zusammendrucke der DDR - Plattenfehler und sonstige Druckzufälligkeiten, 6. Auflage (Combinations of the DDR - Plate Flaws and Other Printing Errors, 6th Edition)

Berlin
Schantl Plattenfehler Katalog Berliner Bauten I, 1949-1958, 5. Auflage (Schantl Plate Flaw Catalog of the Berlin Buildings Issues, 1949-1958, 5th Edition)
Michel Die Bautenserie 1948 (Michel The Buildings Series of 1948)
Philotax Bund+Berlin Plattenfehler-Katalog, 2. Auflage (Philotax Plate Flaw Catalog of the BRD and Berlin, 2nd Edition)
Philotax Bund+Berlin Plattenfehler-Katalog, 1. Ergänzung zur 2. Auflage (Philotax Plate Flaw Catalog of the BRD and Berlin, 2nd Edition, 1st Supplement)
Philotax Bund+Berlin Plattenfehler-Katalog, 2. Ergänzung zur 2. Auflage (Philotax Plate Flaw Catalog of the BRD and Berlin, 2nd Edition, 2st Supplement)