1. M. Poulain, J. Non-Cryst. Solids, 184 (1995) 103.
2. M. Matecki, M. Poulain and T. Izumitani, Mat. Sei. For., 67–68 (1991) 233.
3. D. R. MacFarlane in “Fluoride Glasses”, A. Comyns Ed., J. Wiley & Sons, Chichester, 1989.
4. H. Hu, F. Yuan and J. Feng, Mat. Sci. For., 67–68 (1991) 239.
5. M. Poulain, J. Non-Cryst. Solids, 140 (1992) 1.