are presented here. As topological questions playa role in non-standard theories as weIl, it will be found that some of the lectures and seminar talks in this volume adopt the point of view of standard relativity, whereas others are based on different theories, such as Kaluza- Klein theories, bimetric theories, and supergravity. We have found it difficult to organize these papers into classes, say standard and non-standard theory, or models with and without singularities. One paper, by R. Reasenberg, is experimental. Its purpose was to give the theorists present an inkling of the opportunities, as weIl as the pitfalls, of experimental research in gravitational physics. Accordingly, we have arranged all contributions alphabetically, by ~first-named) author.