I mis stated the authors on "The Mauser Parabellum". It's Don Hallock and Joop van de Kant.
You'll find references on this site, but right now I believe that the book is available directly from the authors. Amazon is also listing resellers of the book.
This thread on Jan Still's site has details:
http://luger.gunboards.com/showthread.php?t=22209
The books are costly because of the expense publishing them and the limited market. They are worth the money. You'll find them somewhat repetitive as they go through all the variations of Lugers, but you'll also have excellent references to work from.
Marc
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Igitur si vis pacem, para bellum -
- Therefore if you want peace, prepare for war.