Bonnell, Jane; Philip Perman, Edgar (1921). "CCXXIX.—The colour of iron alum". J. Chem. Soc., Trans. 119: 1994-1997. doi:10.1039/CT9211901994''. (engelsk)
Cooke, Meyer; Wolf. "The Specific Heats of Three Paramagnetic salts at Very Low Temperatures". Proceedings of the Royal Society of London. Series A, Mathematical and Physical Sciences. 237 (1210): 395-403. doi:10.1098/rspa.1956.0185. (engelsk)