This volume contains the lectures given at the Nordic Summer School in Mathematics 1976, as well as the papers reported on in the adjoint sym­ posium. The Summer School was the 9th in the series sponsored by Nordic Research Courses of the Nordic Cultural Commission. The symposium organized in conjunction with the Summer School was made possible through grants from the Norwegian Research Council for Science and Humanities (NA VF). It is definite that the full project could not have succeeded without the support of both organizations, and I would here like to thank the Nordic Cultural Commission and the Norwegian Research Council for making it possible. The present book contains nearly all talks given at the meeting with one notable exception: The elegant exposition of John Mather on the genericity and finite type of the topologically stable maps was not written up in time to be included in the book. The loss is partly made up for by two recent expositions in the Springer Lecture Notes (No. 535 and 552), which, however, both differ from the presentation given at the Summer School. It is to be hoped that Mather's proof will appear ultimately. Finally I take this opportunity to express my gratitude to the staff of the Mathematics Institute, in particular to Mrs Kirkaloff and Mrs Moller.