During the period under review two issues of the Astronomical Yearbook of the U.S.S.R. for the years 1971, 1972 have been published, and that for 1973 is in preparation. The positions and proper motions of the stars are in the FK4 system as recommended by Commission 4 in 1961. Further, as recommended at the meeting in Hamburg in 1964 (Trans. IAU, 12 B (1964), 105,1966) the IAU System of Astronomical Constants has been introduced into the tabulations of the day numbers, solar and lunar eclipses, ephemerides for physical observations of planets, and the factors S &C. The corresponding differential corrections to the Moon’s ephemeris as well as re-calculated eclipse data for 1971 have been tabulated separately in the Appendix to the Yearbook for 1971. As from the edition of the Yearbook for 1972, the lunar ephemeris j = 2 will be published in accordance with the recommendations adopted in Prague in 1967.

The regular publication of the ephemeris of the lunar crater Mösting A has been continued in the editions of the Yearbook mentioned above.

Fundamental ephemerides of the Sun, Moon, and planets have been printed in full conformity with the first part of the Astronomical Ephemeris circulated in advance by H. M. Nautical Almanac Office, Royal Greenwich Observatory.