1. G. Engelhardt, D. Michel, High-Resolution Solid-State NMR of Silicates and Zeolites (Wiley, Chichester, 1987)
2. W.M. Meier, Z. Kristallogr. 113, 430 (1960)
3. B.H. Torrie, I.D. Brown, H.E. Petch, Can. J. Phys. 42(229), 229 (1964)
4. F. Pechar, W. Schafer, G. Will, Z. Kristallog. 164, 19 (1983)
5. G. Artioli, J.V. Smith, A. Kvick, Acta. Cryst. 40, 1658 (1984)