[1] Μ. B. Wall; Opt, and Laser Technology, 1969, 1 266.
[2] P. Hariharan; Appl. Opt., 1973, 12, No. 1, 143.
[3] C. S. Vikram, G. S. Bhatnagar; Appl. Opt.,1973, 12, No. 10, 2239.
[4] J. Janta, M. Miler; Optiky 1972, 36, 185.
[5] C. S. Vikram; Optik, 1975, 39, 361.