1. M. Ohtaki, T. Tsubota, K. Eguchi, and H. Arai, J. Appl. Phys. 79, 1816 (1996).
2. T. Tsubota, M. Ohtaki, K. Eguchi, and H. Arai, Proceedings of the 16th International Conference on Thermoelectrics (1997), p. 240.
3. T. Tsubota, M. Ohtaki, K. Eguchi, and H. Arai, J. Mater. Chem. 7, 85 (1997).
4. G.A. Slack, Phys. Rev. B 6, 3791 (1972).
5. M. Ohtaki, T. Tsubota, and K. Eguchi, Proceedings of the 17th International Conference on Thermoelectrics (1998), p. 610.