Proceedings of a Workshop held at INRIA, Sophia-Antipolis, France, December 10-14, 1984

Proceedings of a Seminar Series held at DAPHE, Observatoire de Meudon, and LPTHE, Université Pierre et Marie Curie, Paris, Between October 1983 and October 1984

Lectures Given at the 2nd 1982 Session of the Centro Internationale Matematico Estivo (C.I.M.E.) held at Noto, Italy, June 23 - July 2, 1982

Eine Einführung

Proceedings of a Workshop held at the Harvard-Smithsonian Center for Astrophysics. September 27-28, 1984

Proceedings of an International Conference Held at the Massachusetts Institute of Technology, Cambridge, MA, June 13-15, 1984