1. Ables, J. G., Komesaroff, M. M., and Hamilton, P. A.: Astrophys. Letters
6, 147 (1970).
2. Aitken, D. K. and Polden, P. G.: Nature Phys. Sci. 233, 45 (1971).
3. Albats, P., Frye, G. M., Jr., Zych, A. D., Mace, O. B., Hopper, V. D., and Thomas, J. A.: Nature
240, 221 (1972).
4. Alekseev, Y. I., Vitkevitch, V. V., and Malofeev, V. M.: Nature Phys. Sci. 235, 167 (1972).
5. Alekseev, Y. I., Vitkevitch, V. V., Zhuravlev, V., and Shitov, Yu. P.: IAU Circ., No. 2123 (1968).