1) Britannica, The Editors of Encyclopaedia. “Snowball Earth hypothesis.” Encyclopedia Britannica, 21 Nov. 2014, www.britannica.com/science/Snowball-Earth-hypothesis.
2) “Oceans of Ice: The Snowball Earth Theory of Global Glaciation.” Dartmouth Undergraduate Journal of Science, 30 May 2010, sites.dartmouth.edu/dujs/2010/05/30/oceans-of-ice-the-snowball-earth-theory-of-global-glaciation.
3) Schirber, Michael. “Snowball Earth Might Have Been Slushy.” NASA, NASA, Aug. 2015, www.giss.nasa.gov/research/features/201508_slushball/.
4) “Scientists Poke Holes in 'Snowball Earth' Hypothesis.” NSF, 29 Sept. 2005, www.nsf.gov/news/news_summ.jsp?cntn_id=104484.
5) Watkins, Thayer. “Snowball Earth: The Discovery of Evidence That the Earth Was Once Frozen Over from Pole to Pole”, circa 2010, www.sjsu.edu/faculty/watkins/snowball.htm.
6) “What Caused the Snowball Earths?” Snowball Earth, www.snowballearth.org/cause.html.