The following is a partial list of the reference materials used in assembling this web page.  More will be added to it as we progress.

Canon Rangefinder Cameras 1933 - 68
by Peter Dechert
Hove Foto Books
ISBN 0-906447-30-5
Its By Corfield It Must Be Good. The Periflex Story.
by John E. Lewis
Ericsen Lewis Publications
ISBN 0-9510211-0-9
Rollei Photography
by Jacob Deschin
Camera Craft Publishing Co. 1953
Leica  A History Illustrating Every Model & Accessory
by Paul-Henry van Hasbroeck
Sotheby Publications
ISBN 0-85667-430-3
Leitz Catalog V-A 1929
E. Leitz, Inc. NY. NY.
Leica Copies
by HPR
Classic Collection Publications
ISBN 1-874485-05-4
Collectors Guide:  Kodak Retina Cameras
Spot Lite Books, Petersen Publishing Co
Complete Nikon System
by Peter Braczko
Silver Pixel Press
ISBN 1-883403-8-5
Zeiss Ikon Cameras 1926 - 1939
by D. B. Tubbs
Hove Books Ltd.
ISBN 1-874707-01-4
Leica  The first 60 years
by G. Rogliatti
Hove Collectors Books
ISBN 1-874707-02-2
McKeown's Cameras 2005 2006
edited by James M. McKeown and Joan C. McKoewn
Centennial Photo Service
ISBN 0-931838-40-1
WEB PAGES (see also links)