I have recently taken over maintenance of some legacy client projects built with Umbraco 6. I have extensive ASP.NET experience but very little with any version of Umbraco. Unfortunately it seems all relevant documentation has been deleted from our.umbraco.com and any links I've been able to find so far that specifically refer to v6 in the URL, are being silently redirected to v7 docs. This is not at all helpful. An Amazon search only revealed one book published specifically on Umbraco, which dates back to 2011 and doesn't specify which version it covers.
Can anyone tell me if there are any comprehensive API documents or even introductory guides on how to use or develop against this particular version?