Pauli letter collection: letter to Arnold Sommerfeld

Pauli talks about his decision to go to Hamburg. He writes about the difficulties of Bohr's theory of the periodic system. He makes observations about equivalent electron orbits. He says that there is a failure in classical mechanics. He comments on the introduction of half-integer values for j and m. He talks about his own work on the anomalious Zeeman-effect and about Heisenberg's theory of doublets.