Pauli letter collection: letter to Werner Heisenberg

Pauli replies to Heisenberg's letter of 13 April. He criticizes his pressing for a premature publication of the work. He is now convinced that some of the field equations have nothing to do with the real nature of the elementary particles. Possibly, at the present stage of quantized field-theories and on the level of special relativity, a theory of elementary particles is impossible without ad hoc assumptions