«Article in Journal of Chemical Education»(PDF). Division of Chemical Education of the American Chemical Society. November 2000. Arkivert frå originalen(PDF; subscription required) 15. september 2006. Henta 27. februar 2011.
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«Article in Journal of Chemical Education»(PDF). Division of Chemical Education of the American Chemical Society. November 2000. Arkivert frå originalen(PDF; subscription required) 15. september 2006. Henta 27. februar 2011.