PMID 16078867. ↑ Jonathan Lunine "Saturn’s Titan: A Strict Test for Life’s Cosmic Ubiquity" (accepted for publication in Proceedings of the American Philosophical Society), July 21, 2009 (Revised November 7, 2009), page 13 ↑ Jonathan Lunine "Saturn’s Titan: A Strict Test for Life’s Cosmic Ubiquity" (accepted for publication in Proceedings of the American Philosophical Society), July 21, 2009 (Revised November 7, 2009), page 18 ↑ Chris Impey (Jan 31, 2011). "Jan 31st: Life on Titan". 365 Days of Astronomy.