Brunvand, Jan Harold. "Alligators in the Sewers." Too Good To Be True.
New York: W. W. Norton and Co., 1999. (pp.182-185).
An update by Brunvand.
Coleman, Loren. "Alligators in the Sewers." Mysterious
America: the Revised Edition. New York: Paraview Press, 2001. (pp. 67-75).
Cryptozoologist Loren Coleman approaches the sewergator legend from a Fortean perspective. A list of his works on displaced crocodilians can be found here.
Daley, Robert. The World Beneath the City.
New York: J. B. Lippincott Co., 1959. (pp. 13, 187-189).
Though intended as a serious work, Daley's account of alligators in the sewers relies entirely on the testimony of the very imaginative Teddy May, and needs to be taken with a large dose of salt. It is, however, the first known written account of the canonical sewergator legend (i.e., baby alligators brought from Florida to New York as pets are flushed into the sewers when they grow too large for safety).
Glasgow, Vaughn L. A Social History of the American Alligator.
New York: St. Martin's Press, 1991. (pp. 15-17).
A short narrative on the legend.
Mikkelson, Barbara. "Gatored Community."
The best study of sewergators to be found on the Net. Contains further references.