1. Alfvén, H.: 1942,Stock. Obs. Ann. 14, No. 2.
2. Alfvén, H. and Arrhenius, G.: 1976,Evolution of the Solar System, N.A.S.A., SP-345.
3. Anders, E. and Owen, T.: 1977,Science 198, 453.
4. Aust, C. and Woolfson, M. M.: 1971,Mon. Not. R. Astr. Soc. 153, 210.
5. Black, D. F.: 1978,The Origin of the Solar System, Ed. S. F. Dermott, J. Wiley Pub. Co.