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2011. <http://www.absoluteastronomy.com/topics/Calcium_sulfate>.
"Calcium Sulfate." Jrank.org. Web. <http://science.jrank.org/pages/1124/Calcium-Sulfate.html>.
"Calcium Sulfate." Wikipedia, the Free Encyclopedia. Web. 13 Dec. 2011
<http://en.wikipedia.org/wiki/Calcium_sulfate>.
"Gypsum Mineral,Hydrated Calcium Sulfate,Gypsum Applications,Gypsum Resources."Mineral Industries,World
Minerals,Mineral Information,Properties of Minerals. Web. 13 Dec. 2011.
<http://www.mineralszone.com/minerals/gypsum.html>.