As any author I am glad to see my book appear in English, a language accessible to all physicists nowadays. However, it is hardly necessary to
wirte a special preface to say this or to mention that in the English edition
a nmber of errors have been corrected. The idea that such a preface might be
necessary arose when I received from Professor ter Haar the preliminary list
of references for the English edition and noticed the large number of
references to Ginzburg. Of course, the same references also appear in the
Russian edition, but there they do not appear together in one lot, and are
also not so obvious in the text. The reason is that in the Russian edition,
as is the usage with us, references are indicated by a number,without mention-
ing the name of the authors. As a result my name never appears in the text,
while in the English translation one meets it very often! Such a situation is
unusual for a book meant for students or, at any rate,one which is not a mono-
graph, and it may cause some unpleasant observations. I want therefore to add
the following to what I said in the preface to the Russian edition. I am, in
general, not a teacher and I do not like to lecture, especially not when the
same material must be presented more than once. At the same time, for the
first time lectures one needs a large amount of preparation. In such a situa-
tion and if I have the possibility to choose the subject of the lectures
completely freely I have given some lectures just once; the present book was
written in preparing such a course. when choosing the material and wishing to
share with my audience or my readers what appeared to me to be interesting and
important I widely used my own papers and review articles. Of course, the
result was a very one-sided picture. However, as there was no pretension of
priority claims to that I had chosen the most interesting problems, there was
hardly any reason for reproaching me of immodesty. A different question is
whether the book is useful and deserving attention, that that is, of course,
up to the reader to decide.