Encyclopedias and dictionaries
Bergmann, Peter G. "Relativity." The New Encyclopaedia Britannica: Macropaedia. 15th ed. 29 vols. Britannica, 2002.
"Cronstedtite." The Oxford English Dictionary. 2nd ed. 1989. OED Online. www.oed.com/view/Entry/44734?redirectedFrom=Cronstedtite#eid. Accessed 14 June 2016.
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