Alexandr A. Borovkov
This book has been written on the basis of the Russian version (1986) published by “Nauka” Publishers in Moscow. A number of sections have been substantially revised and several new chapters have been introduced. The author has striven to provide a complete and logical exposition and simpler and more illustrative proofs. The 1986 text was preceded by two earlier editions (1972 and 1976). The first one appeared as an extended version of lecture notes of the course the author taught at the Department of Mechanics and Mathematics of Novosibirsk State University. Each new edition responded to comments by the readers and was completed with new sections which made the exposition more unified and complete.