This is an educational experience for me--I knew Theta Phi Alpha was in the NPC, but I had never really heard anything about it before now. I wonder, do small campuses generally attract the smaller, lesser-known groups? Not that there's anything wrong with that, of course
, but none of the "big name" sororities were ever at Rio and I'm just wondering if it's because it's small...here, we have a big campus with all the well-known groups, but we don't have any smaller ones. (We had Phi Sig a long time ago, but it's gone now.) I'm just thinking out loud here...
Anyway, I would say e-mailing or calling the sororities' National Headquarters would be the best way to go. The Baird's Manual is good, but as someone mentioned they are hard to find (our main library doesn't even have the latest edition, and it's a HUGE library) and you may not be able to find one that's got the info you want since you would need one published after the 1980s to find out what you want to know.
*Edited to say that I did some detective work (otherwise known as putting off homework as long as possible), and Zeta Theta Chi was Alpha Sigma Tau, and Chi Omega Alpha was Phi Sigma Sigma. So there you go.*