Reading the proceedings of a successful conference which one did not attend is inevitable a somewhat tantalizing experience. Of most immediate concern are those topics lying within one's own area of research. However, interesting such papers may be in their own right, one cannot fail to be aware of lost opportunities for asking probing questions and for picking up new techniques and valuable advice through personal contract with colleagues and rivals from elsewhere. In addition there is, of course, the wider interest engendered by topics of which one knew little, but would certainly have liked to learn more by discussing them at first hand with the relevant specialists. The present volume is no exception.