Where can I find information about the different identity groups founded by Marshall Singer?

I attend an online university, and I have to make a discussion posts about the identity groups talked about by Marshall Singer (1998). Unfortunately, my required readings do not mention anything about it, nor can I find any information about it online. And yes, I did send my professor an email today. For some strange reason, this is the first week of class and she is on vacation. I'm not feeling good about this. Thanks for your help.