1. Jain, D. L., Appl. Sci. Res.24 (1971) 379.
2. Bouwkamp, C. J., Philips Res. Rep.5 (1950) 401.
3. Meixner, J., The behaviour of electromagnetic fields at edges, New York Univ., Inst. of Math. Sci., Div. of Electromagnetic Res., Res. Rep. No. EM-72, December 1954.
4. Thomas, D. P., Canad. J. of Phys.47 (1969) 921.