There is a short description of the technique in the first (1992) edition of the CCPS book Guidelines for Investigating Chemical Process Incidents, on pages 35-37, including some figures and standard symbols. The text attributes the technique to the Electric Power Research Institute (EPRI), and gives a specific reference:

Mosleh, A., et al, 1988, Procedures for Treating Common Cause Failures in Safety and Reliability Studies, EPRI NP-5613, Palo Alto, CA, Electric Power Research Institute.

I do not have this reference, so I can't comment on its value.

There is a 2nd edition of the CCPS book which I do not have, so their text may have changed from the first edition.

I have seen some text on this method in other books on incident investigation which are in the Rohm and Haas library, but I don't have specific references any more. They might try searching other books on investigation.