“Structure Cristalline et Expansion Thermique de L’Iodure de Nickel Hexahydrate“ (Crystal structure and thermal expansion of nickel(II) iodide hexahydrate) Louër, Michele; Grandjean, Daniel; Weigel, Dominique Journal of Solid State Chemistry (1973), 7(2), 222-8. doi: 10.1016/0022-4596(73)90157-6.
dx.doi.org
B. Morosin "An X-ray diffraction study on nickel(II) chloride dihydrate" Acta Cryst. 1967. volume 23, pp. 630-634. DOI:10.1107/S0365110X67003305