1. G. R. Bishop andR. Wilson:Handb. der Phys.,42 (Berlin, 1957), p. 315; or R. G. Sachs and N. Austern:Phys. Rev.,81, 705 (1951).
2. The Siegert theorem is discussed in great detail inG. R. Sachs:Nuclear Theory (Cambridge, 1953), p. 242; or in J. S. Levingee:Nuclear Photoeffecls (London, 1960).
3. N. Austern andE. Rost:Phys. Rev.,117, 1506 (1960).
4. B. Bosco, G. Ciocchetti andA. Molinari:Nuovo Cimento,28, 1427 (1963).
5. G. A. Peterson andW. C. Barber:Phys. Rev.,128, 812 (1962).