1. D. T. Wilkinson and H. R. Crane:Phys. Rev.,130, 852 (1963); W. H. Louisell, E. W. Pidd and H. E. Crane:Phys. Rev.,94, 7 (1954).
2. K. Ziock, V. W. Hughes, E. Prepost, J. Bailey and W. Cleland:Phys. Rev. Lett.,8, 103 (1962); G. Backenstoss, K. Goebel, U. Hegel, D. Quitmann and B. Stadler:Nucl. Phys. (in press).
3. A. Petermann:Helv. Phys. Acta,30, 407 (1957). A complete list of references is given in a review by A. Petermann:Fortschr. d. Phys.,6, 505 (1958). The numerical coefficient of the second term has now been evaluated for more precisely, Petermann: (private communication).
4. V. B. Beeestetskij, O. N. Krokhin and A. K. Khlebnikov:Zum. Ėksp. Tear. Fiz.,30, 788 (1950) [translation:Soviet Physics JETP,12,993 (1961)].
5. R. L. Garwin, L. M. Ledeeman and M. Weineich:Phys. Rev.,105, 1415 (1957).