1. T. H. Etsell and S. N. Flengas, Chem. Rev. 70 (1970) 339.
2. D. Yuan and F. A. Kr�ger, J. Electrochem. Soc. 116 (1969) 594.
3. H. Obayashi and T. Kudo, in ?Solid State Chemistry of Energy Conversion and Storage?, Advances in Chemistry Series, Vol. 163, edited by J. B. Goodenough and M. S. Whittingham (The American Chemical Society, Washington, D.C., 1977) p. 316.
4. N. M. Beekmans and L. Heyne, Electrochim. Acta 21 (1976) 303.
5. M. Kleitz, H. Bernard, E. Fernandez and E. Shouler, in ?Advances in Ceramics?, Vol. 3, edited by A. H. Heuer and L. W. Hobbs (The American Ceramic Society, Columbus, Ohio, 1981) p. 310.