1. Multinuclear NMR, Ed. by J. Mason (Plenum, New York, 1987).
2. L. V. Dmitrieva, L. S. Vorotilova, and M. V. Razumeenko, Fiz. Tverd. Tela (St. Petersburg) 39, 1194 (1997) [Phys. Solid State 39, 1057 (1997)]; L. V. Dmitrieva, L. S. Vorotilova, I. S. Podkorytov, and M. G. Shelyapina, Fiz. Tverd. Tela (St. Petersburg) 41, 1204 (1999) [Phys. Solid State 41, 1097 (1999)].
3. O. Kanert and H. Schulz, Solid State Commun. 91, 465 (1994).
4. T. J. Bastow, J. Phys.: Condens. Matter 1, 4985 (1989).
5. J. A. Tossell, J. Magn. Reson. 94, 301 (1991).