1. Braunbek, W. and Laukien, G. (1952).Optik,9, 174.
2. Sommerfeld, A. (1954).Lectures on Theoretical Physics, Vol. 4, Ch. 5, pp. 247–72. Academic Press, New York. (Note: Sommerfeld's solution for the semi-infinite plane was originally published in German in 1896 inMath. Ann. 47, 317.)