1. Über die Theorie des Kreisels;Klein,1965
2. Über die Theorie des Kreisels;Klein,1965
3. Theoretische Mechanik;Hamel,1967
4. Linear and regular celestial mechanics;Stiefel,1971
5. J. Baumgarte, Numerical stabilization of the differential equations of Keplerian motion, to appear in “Celestial Mechanics”.