1. R. S. Berry, Lectures, Proc. Mt. School Phys. “Enrico Fermi,” 44, 193 (1970), Academic Press, New York.
2. A. Fontijn, in “Progress in Reaction Kinetics” (G. Porter, ed.), Vol. 6, Pergamon Press, New York (1971).
3. R. C. Williamson, Phys. Rev. 21, 107 (1923).
4. R. Samuel, Z. Physik. 29, 209 (1924).
5. J. Kunz and E. H. Williams, Phys. Rev. 22, 456 (1923).