

Some more references:

S.H. Dole

"Habitable Planets for Man"
Blaisdell Publishing Company, New York (1964)

I don't know if this can be found any more.

M.J. Fogg

"Extra-Solar Planetary Systems: A Microcomputer Simulation"
J. Brit. Interplanetary. Soc., _38_, 501-514, (1985)

"An Estimate of the Prevalence of Biocompatible and Habitable Planets"
J. Brit. Interplanetary. Soc., _45_, 3-12, (1992)

The first paper includes a detailed discussion of the physical conditions
for habitability.
