This report covers the period July 1, 1987, to about June 30, 1990. The task of preparing the individual sections has been carried mainly by members of the Organizing Committee and chairmen of the Working Groups. All authors have to be thanked for this service to the community. The authors were free to emphasize what seemed important to them, rather than to attempt completeness. It is hoped that the abbreviated references are self-explanatory; in some cases the code numbers of Astronomy and Astrophysics Abstracts are used. A + sign stands for et alii.