1. V. S. Safronov, Evolution of a Protoplanetary Cloud and the Formation of the Earth and Planets (Nauka, Moscow, 1969) [in Russian].
2. M. Laplace, Exposition du système du monde, 3rd Ed. (Chez Courcier, Paris, 1808; Obshchestvennaya Pol’za, St. Petersburg, 1861), Vols. 1, 2.
3. F. Hoyle, Quart. J. Roy. Astron. Soc. 1, 28 (1960).
4. O. Struve, Astrophys. J. 73, 94 (1931).
5. G. P. Kuiper, Astrophys. J. 93, 133 (1941).