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 Iiterature in all fie1ds of astronomy and astrophysics. Every effort will be made to ensure that the average time interval between the date of receipt of the original Iiterature 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 10 contains Iiterature published in 1973 and received before March 15, 1974; some older Iiterature which was received late and which is not recorded in earlier vo1umes is also included. We acknowledge with thanks contributions to this volume by Dr. J. BouSka, who surveyed journals and publications in the Czech language and supplied us with abstracts in English, and by the Common­ wealth Scientific and Industrial Research Organization (C.S.I.R.O.), Sydney, for providing titles and abstracts of papers on radio astronomy.