Sources:

Angela and Henning von Einem Leica I mod.A variations - Hengela@aol.com
Filippo Giunta Leica Screw Mount Cameras - A Systematic Approach ISBN 978-3-89506-147-9
Willy Hahne Hahne Liste
Theo Kisselbach The LEICA Book
James Lager Leica: An Illustrated History. Cameras, Lenses and Accessories ISBN 0963697323 - ISBN 9780963697325 - ISBN 9780871001610 = ISBN 0871001616
Dennis Laney's Leica 1984 Accessory Guide (1st edition) courtesy of Mike Butkus
2nd Edition 2006 Reprint: ISBN 1-874707-26-X
Willard D. Morgan; Henry M. Lester Internet Archive: Free Download: The Leica Manual A Manual For The Amateur And Professional Covering The Entire Field Of Leica Photography (1937 - text only file) - PDF Version (large file with pictures)
Gunter Osterloh Leica M Advanced Photo School ISBN 9781579906375
William White Photomacrography - An Introduction - Focal Press 1987 ISBN 0-240-51189-1

The Fontenelle Collection

Media:The_Fontenelle_Collection_-_Doc.pdf - Pierre Jeandrain's comprehensive list of Leitz and Leica publications from his collection.