1. Crystallography and Crystal Chemistry of Materials with Layered Structure, ed. F. Lévy, Reidel, Dordrecht-Boston, 1976;
2. F. Jellinek , in Inorganic Sulphur Chemistry, ed. G. Nickless, Elsevier, Amsterdam, 1968, p. 669.
3. F. Wypych and R.Schöllhorn, unpublished work.