Hacker, Barton C., and Gordon B. Chamberlain. "Pasts that Might Have Been"
Comments: Bibliography of alternate histories published before 1981.
Published: In Extrapolation Winter 1981.

Hacker, Barton C., and Gordon B. Chamberlain. "Pasts that Might Have Been, II: A Revised Bibliography of Alternative History"
Comments: 61-page listing of alternate histories published before 1986, with short synopses and publication histories.
Published: In w88 android (eds. Charles G. Waugh and Martin H. Greenberg), q.v.