1. Aldrovandi, R. and Caser, S.: 1972, Nucl. Phys.
B38, 593.
2. Alfvén, H. and Klein, O.: 1962, Arkiv Fysik
23, 187.
3. Cisneros, A.: 1972, California Institute of Technology Thesis (to be published).
4. Dashen, R., Ma, S., and Bernstein, H. J.: 1969, Phys. Rev.
187, 345.
5. Kundt, W.: 1971, A Survey of Cosmology, Springer Tracts, Heidelberg.