1. Sperry Gyroscope Company, “Microwave transmission design data” (Publication No. 23–80), p. 117.
2. The problem considered here has been treated by another method in an unpublished paper by Dr. J. Schwinger.
3. J. A. Stratton,Electromagnetic Theory(McGraw-Hill Book Company, Inc., New York, 1941), first edition, p. 360.