1. F. A. MUMPTON, in: Natural Zeolites, L. B. SAND, F. A. MUMPTON, (Eds), Pergamon, Oxford, 1978, p. 3.
2. D. E. W. VAUGHAN, in: Natural Zeolites, L. B. SAND, F. A. MUMPTON, (Eds), Pergamon, Oxford, 1978, p. 353.
3. D. W. BRECK, in: Properties and Applications of Zeolites, R. P. TOWNSEND (Ed.), Chem. Soc. Spec. Publ. No. 33, UK, 1980, p. 391.
4. A. DYER, Chem. Ind., 2 April (1984) 241.
5. J.-P. ROCCI, Les Zeolites, BRGM 87 SGN 183 GEO, 1987.