1. FRIEND, J.N.: A Text Book of Inorganic Chemistry Vol. V, p. 428, Charles Griffin & Co., London, 1921.
2. PERRE, L. and M. JAULMES: Compt. rend. acad. agr. France, 34 864 (1948).
3. Powder Diffraction File Search Manual, 1973, published by the Joint Committee on Powder Diffraction Standards, Swarthmore, Pennsy., U.S.A.
4. U.S. DEPT. HEW: Drinking Water Standards. PHS Pub. No. 956 (1962). 6