Training Manual . - M. : Science, 1971. — 288 s. : il. — 530. 1, L 55, UDC 530. 145. The book is the 4th volume widely known both here and abroad, and the course of theoretical physics L. awarded the Lenin Prize. D. Landau and E. M. Lifshitz . Part I of the book presents the relativistic theory of free particles, particles in the external field, the theory of light scattering, the relativistic theory of perturbations and its application to electrodynamic processes. The first three chapters of Part II of the book are devoted to the theory of radiation corrections and complete the presentation of quantum electrodynamics. The theory of weak interactions and some questions of the theory of strong interactions. are presented below. The authors sought not only to emphasize the fundamental foundations of the methods used, but also to identify the essential technical details; therefore, specific calculations are presented with a relatively large degree of detail. According to the original plan of L. D. Landau, this course should only present those theoretical results that appear to be reasonably well established and fit into a particular system. In other words, the presentation should not get too close to the “front edge” of theoretical physics. The application of this criterion at the present time is, of course, particularly difficult in such areas as the theory of weak and strong interactions. In addition, the decomposition of separate disparate information would hardly be useful for those who are specifically interested in this area, and could not be interesting for others. Based on these considerations, we have decided to confine ourselves in this book to a small one: the dynamic symmetry of strong interactions and the “phenomenological” theory of weak interactions. We hope that even with such limited content, the book can still be useful to a sufficiently wide range of readers.