1. Keppens, V. et al. Nature 395, 876–878 (1998).
2. Mahan, G. D. in Solid State Physics Vol. 51 (eds Ehrenreich, H. & Spaepen, F.) 82-158 (Academic, San Diego, 1998).
3. Slack, G. A. in CRC Handbook of Thermoelectrics (ed. Rowe, D. M.) 407-440 (CRC Press, Boca Raton, 1995).
4. Slack, G. A. & Tsoukala, V. G. J. Appl. Phys. 76, 1665–1671 (1994).
5. Nolas, G. S., Cohn, J. L. & Slack, G. A. Phys. Rev. B 58, 164–170 (1998).