1. F. Calogero:Nuovo Cimento,27, 261, 1007 (1963). These will be referred to as I and II respectively. Earlier references to the phase method are given in I.
2. F. Calogero:Nuovo Cimento,28, 320 (1963).
3. G. Parzen:Phys. Rev.,80, 261 (1950).
4. C. Schwartz (private communication) had previously compared the two methods for a Yukawa potential, with similar magnitudes for the range, strength and wave number. He also found that the phase method is more accurate than the usual wave-equation approach.
5. See, for example,J. B. Scarborough:Numerical Mathematical Analysis, 2nd Ed. (Oxford, 1950), p. 299.