References
- Ankiewicz , A. and Pask , C. 1977 . Geometric optics approach to light acceptance and propagation in graded index fibres . Opt, and Quant. Electron , 9 : 87 – 109 .
- Ralston , A. and Rabinowitz , P. 1978 . A First Course in Numerical Analysis , New York : McGraw-Hill .