I've just seen this Thread and I'm not going to read it all (!), so if the following has already been mentioned, please forgive.

A DVD, 'Pete Seeger's Rainbow Quest - New Lost City Ramblers and Greenbriar Boys. Two classic shows from the 60s - 2 hours' was released in 2005. Contains some great music and interviews with the lads. A book by Bob Yellin was mentioned but I've haven't been able to trace it.