1. Bhutani, O. P. and K. D. Nanda, AIAA J. 6 No. 9 (1968) 1757.
2. Bhutani, O. P. and R. Sharma, J. Math. Anal. Appl. 18 (1967) 119.
3. Coburn, N., J. Math. Anal. Appl. 5 (1962) 269.
4. Vincenti, W. G. and C. H. Kruger, Introduction to Physical Gasdynamics, John Wiley and Sons, Inc., 1965.
5. Weatherburn, C. W., Differential Geometry of three dimensions, Vol. I, Cambridge Univ. Press, Cambridge, 1955.