Sources:

• Dennis Laney's Leica 1984 Accessory Guide (1st edition) courtesy of Mike Butkus
  2nd Edition 2006 Reprint: ISBN 1-874707-26-X
• Filippo Giunta Leica Screw Mount Cameras - A Systematic Approach ISBN 978-3-89506-147-9
• William White Photomacrography - An Introduction - Focal Press 1987 ISBN 0-240-51189-1
• Theo Kisselbach The LEICA Book
• Willy Hahne Hahne Liste
• James Lager Leica: An Illustrated History. Cameras, Lenses and Accessories ISBN 0963697323 ISBN 9780963697325 ISBN 9780871001610 ISBN 0871001616
• Gunter Osterloh Leica M Advanced Photo School ISBN 9781579906375
• 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)
• Angela and Henning von Einem Leica I mod.A variations - Hengela@aol.com