References
- Elliott , R. J. 1957 . Phys. Rev. , 108 : 1384
- Sturge , M. D. 1962 . Phys. Rev. , 127 : 768
- Goñi , A. R. , Strössner , K. , Syassen , K. and Cardona , M. 1987 . Phys. Rev. B , 36 : 1581 and references therein
- Reimann , K. and Syassen , K. 1989 . Phys. Rev. B , 39 : 11113
- Toyozawa , Y. 1958 . Prog. Theo. Phys. , 20 : 53
- Sell , D. D. and Lawaetz , P. 1971 . Phys. Rev. Lett. , 26 : 311
- Sell , D. D. 1972 . Phys. Rev. B , 6 : 3750
- Cardona , M. 1972 . Atomic Structure and Properties of Solids , Edited by: Burnstein , E. New York : Academic Press .
- Conwell , E. M. 1967 . High Field Transport in Semiconductors , New York : Academic Press .