1. G. N. Duboshin: 1976, Celestial Mechanics,, 14 239
2. M. Z. Aboelnaga and Y. V. Barkin: 1979, Astronom. Zh., 56, 881
3. Y V. Barkin: 1980, Pis’ma Astron. Zh., 6, 377
4. L. Wang, P. S. Krishnaprasad and J. H. Maddocks: 1991, Celestial Mech., 50, 349
5. L. Wang and P. Chen: 1995, IEEE Transactions on Automatic Control, 10, 1732