1. Supplied by Bell Telephone Laboratories, Murray Hill, New Jersey, and Magnetic Metals Company, Camden, New Jersey.
2. For formulas, see P. M. Morse,Vibrations and Sound(McGraw-Hill Book Company, Inc., New York, 1948), p. 208.
3. For a more complete discussion see G. Joos,Theoretical Physics(Hafner Publishing Company, Inc., New York, 1934), p. 93.