Possible evidence of the nickel nitrate salt Ni(NO3)2 . 5.5 H2O R. Metz, C. Machado, R. Tenu, M. Elkhatib, J.M. Letoffe and H. Delalu J. Phys. IV France, 113 (2004) 139-142 DOI: 10.1051/jp4:20040030