1 “... the essence of a great mathema­ tical physicist concentrated into one convenient volume. Weyl, Yang and Lieb...”

2 “... because the necessary mathe­ matical methods are being developed and become known to the physicists slowly...”

3 “... appearance of this textbook have since become the everyday tools of working physicists. This new edition...”

4 “...-semester course I offered to both mathematicians and physicists, who were only required to have taken...”