411 REFERENCE · Wikibooks
Extraterrestrial Life/Bibliography
Reference material by Wikibooks contributors. This retains its source identity and is not 411 news reporting.
Habitable Planets. Retrieved from http://ircamera.as.arizona.edu/NatSci102/NatSci102/lectures/habzone.htm
What Makes a World Habitable? Retrieved from http://www.lpi.usra.edu/education/explore/our_place/hab_ref_table.pdf