1. A. Sommerfeld:Phys. Zeits.,8, 841 (1907).
2. See for more detailsA. Sommerfeld:Ann. der Phys.,44, 177 (1914).
3. H. A. Kramers:Nature,117, 775 (1925);Atti del Congresso Internazionale dei Fisici, Vol.2 (Como, 1927), p. 545;R. de L. Kronig:Journ. Opt. Soc. Am.,12, 547 (1926).
4. H. Rechenberg:Optical dispersion relations with finite wave packets, Austin preprint (AEC 91-CPT 144) (June, 1972).
5. H. Rechenberg andE. C. G. Sudarshan:Nuovo Cimento,12 A, 541 (1972), quoted as I below.