[Air-l] History of Instant Messaging

I'm trying to track the history of modern instant messaging (including ICQ, America Online, Yahoo, and MSN). In particular, I'm looking for the dates when each first appeared (ICQ is the only one I've managed to track: 1996). Does anyone have any historical info? Thanks for the help. Naomi Naomi Baron Professor of Linguistics American University Washington, DC 20016-8045