Deviation of A2B6 compounds from stoichiometry : electroneutral defects or the adsorption of one component excess?Lott, Kalju; Grebennik, Andrey; Dontsova, Aleksandra; Raukas, Maie; Vishnyakov, AnatolyProceedings of the Estonian Academy of Sciences. Chemistry1995 / 2/3, p. 114-117