Pauli letter collection: letter to Werner Heisenberg

Pauli writes of his definite decision not to publish together with Heisenberg paper "On the isospin group in the theory of elementary particles", because essential parts of the pre print cannot be backed by him. He says that free to publish the paper alone. He summarizes his own views: 1)out of the degeneracy of the vacuum the possibility of a half-integer difference between ordinary spin and isospin cannot be concluded. 2)The idea of unification of field for strange particles has failed. 3)The eigenvalue problem has not been solved. 4)The physical meaning of the indefinite metric has not been clarified.