Physicists actively engaged in advanced research should be en couraged to discuss results and deepen their theoretical understand ing of the data. It is practically impossible nowadays to achieve the goal of the old times when small groups of scientists had the privilege of debating their ideas and the details of their experi ments in an informal and friendly way. Conferences are now too wide in scientific coverage and, in consequence, there are often too many participants. The Highly Specialized Seminars of the Ettore Majorana Centre for Scientific Culture are intended to provide such a forum for scientists of outstanding reputation in their fields to exchange information. This volume deals with one of the most interesting topics in subnuclear physics, and Professor Giuliano Preparata is one of the world's leaders in the field. This volume contains the most recent results on the study of deep inelastic phenomena, using neutrinos, muons and electrons against nucleons, and (e+e- ) interactions. It represents our best knowledge of the field as given by some of the most distinguished world experts in the theoretical and experimental domain. Antonino Zichichi, Director Ettore Majorana Centre for Scientific Culture v PREFACE In March 1979, about 50 physicists gathered in Erice to parti cipate in the Fourth Highly Specialized Seminar on "Probing Hadrons with Leptons."