Astronomy and Astrophysics Abstracts. which appears in semi-annual volumes, is devoted to the re cording, summarizing and indexing of astronomical publications throughout the world. It is prepared under the auspices of the International Astronomical Union (according to a resolution adopted at the 14th General Assembly in 1970). Astronomy and Astrophysics Abstracts aims to present a comprehensive documentation of literature in all fields of astronomy and astrophysics. Every effort will be made to ensure that the average time interval between the date of receipt of the original literature and publication of the abstracts will not exceed eight months. This time interval is near to that achieved by monthly abstracting journals, com pared to which our system of accumulating abstracts for about six months offers the advantage of greater convenience for the user. Volume 3 contains literature published in 1970 and received before August IS, 1970; some older lite rature which was received late and which is not recorded in earlier volumes is also included.

Astronomy and Astrophysics Abstracts, which has appeared in semi-annual volumes since 1969, is de voted to the recording, summarizing and indexing of astronomical publications throughout the world. It is prepared under the auspices of the International Astronomical Union (according to a resolution adopted at the 14th General Assembly in 1970). Astronomy and Astrophysics Abstracts aims to present a comprehensive documentation of literature in all fields of astronomy and astrophysics. Every effort will be made to ensure that the average time interval between the date of receipt of the original literature and publication of the abstracts will not exceed eight months. This time interval is near to that achieved by monthly abstracting journals, com pared to which our system of accumulating abstracts for about six months offers the advantage of greater convenience for the user. Volume 18 contains literature published in 1976 and received before March 1, 1977; some older liter ature which was received late and which is not recorded in earlier volumes is also included.

Astronomy and Astrophysics Abstracts, which appears in semi-annual volumes, is devoted to the re cording, summarizing and indexing of astronomical publications throughout the world. It aims to pre sent a comprehensive documentation of literature in all fields of astronomy and astrophysics. Every effort will be made to ensure that the average time interval between the date of receipt of the original literature and publication of the abstracts will not exceed eight months. This time interval is near to that achieved by monthly issued abstracting journals, compared to which our system of accumulating abstracts for about six months offers the advantage of greater convenience for the user. Volume 2 contains literature published in 1969 and received before March 15, 1970; some older lite rature which was received late and which is not recorded in Volume 1 is also included. The authors of papers who have sent us abstracts on request have effectively contributed to the suc cess of our service. We should like to express our gratitude to them. We acknowledge with thanks con tributions to this volume by Dr. J. Bou~a, who surveyed journals and publications in Czech language and supplied us with abstracts in English, by Dr. B. Onderlicka, Brno, for providing English ab stracts of Russian papers, and by the Commonwealth Scientific and Industrial Research Organization (C.S.I.R.O.), Sydney, for providing titles and abstracts of papers on radio astronomy.