[5] G. E. Albert, and J. L. Synge, “The General Problem of Antenna Radiation and the Fundamental Integral Equation, with Application to an Antenna of Revolution – Part I”, Quart. Appl. Math. , vol. 6, no. 2, pp. 117-131, 1948. [Online]. Available: https://www.jstor.org/stable/43633659