Contax System Information
The Zeiss Data Sheet Download Page – Downloadable data sheets for the Zeiss lens range.
The Contax UK page – There’s a ton of info available about the lens rand and late model cameras
Tom Shea’s 1998 overview of many Zeiss/Contax lenses at Photo.net (lots of good comments on this page)
A Long and informative Thread at Photo.net (There are however a couple of inaccuracies e.g. my 300/4 MMG shouldn’t exist if everything here was true).
An Epic Thread at Reduser.net but be aware that there are a ton of inaccuracies here on the detail of the AE/MM business.