I am very happy to accept the translators' invitation to write a few lines of introduction to this book. Of course, there is little need to explain the author. Pauli's first famous work, his article on the theory of relativity in the Encyc opiidie der Mathematischen Wissenschaften was written at the age of twenty. He afterwards took part in the development of atomic physics from the still essentially classical picture of Bohr's early work to the true quantum mechanics. Thereaftt'f, some of his work concerned the treatment of problems in the framework of the new theory, especially his paper on...