1. F. S. Peres, in: Geological Structure and Mineral Resources of the Moldavian SSR [in Russian], Shtinitsa, Kishinev (1976), p. 59.
2. F. S. Peres, Izv. Akad. Nauk MSSR, Ser. Fiz-Tekhn, i Mat. Nauk., No. 3, 81 (1977).
3. A. G. Kozlova, Izv. Vuzov, Ser. "Stroitel'stvo i arkhitektura", No. 1, 77 (1983).
4. P. S. Aggarwal, N. C. Bisuras, and B. L. Mitra, Central Glass and Ceramic Research Institute Bulletin,29, No. 1, 22 (1982).