Pauli letter collection: letter to Markus Fierz

Pauli writes on the importance of a paper by Coester, published in: Physical review: 83 (1951), for the problem of the transition from neutral vector mesons to quantum electrodynamics. He explains the connection of this paper with that of four Japanese physicists, published in: Progress of theoretical physics: 6 (1951) on the possibiliy of avoiding indefinite metric in Hilbert-space in quantum electrodynamics.