volume XIX A of IAU Transactions contains the reports by Presidents of
Commissions, covering the period July 1981 - June 1984. The topics of
IAU Commissions deal with all of contemporary astronomy and the present
volume therefore constitutes an exhaustive and unique record of
astronomical research during this interval. It is particularly useful
for astronomers and other scientists who want to gain an overview of a
certain field, not necessarily near their own research area. Each
Commission President was requested, by early 1984, to begin prep-
arations for the compilation of his/her Commission report. All members
of Commissions were asked to supply details about their individual
research pro- grammes. The ensuing, very substantial task of
concatenating was undertaken in late 1984 by the Presidents, often
supported by a team of authors, all recog- nized authorities in their
fields. In order to preserve some measure of uni- formity - which is in
any case very difficult with so many authors - editorial guidelines were
sent to Presidents, including the number of pages allotted to each
Commission.