1. Y. T. Shah, Sc.D. Dissertation, Massachusetts Institute of Technology, Cambridge, Massachusetts (1968).
2. J. E. White, Ph.D. Thesis, University of Kentucky, Lexington, Kentucky (1973).
3. J. H. Skorupski, M.S. Thesis, University of Kentucky, Lexington, Kentucky (1974).
4. O. H. Nestor and H. N. Olsen, SIAM Rev. 2: 200 (1960).
5. C. J. Cremers and R. C. Birkebak, Appl. Optics
5 (6): 1057 (1966).