Pauli comments on a letter by Källén and his problem of two N-particles.

Pauli gives a more precise formulation to the problem of dipole ghosts and an another solution. He also discusses approximation through complex roots.

Pauli writes on a correspondence with Heisenberg on his ideas on field quantization.

Pauli replies to Källén's letter of the 10 and the 12 January 1957. He talks about of his discussion with Fierz of the time-dependent solutions for dipole ghosts. Fierz criticizes Pauli's continuity argument for the S-matrix.

Pauli writes of his reactions to the experiments showing parity violation. He gives reasons for his doubt of this possibility up to now. The main problem is now: why are the strong interactions reflexion-invariant? Pauli makes some general considerations on TCP-invariance.

Pauli makes a critical comment on Fierz's paper on Jordan's theory.

Pauli talks more about the indefinite metric which Pauli rejects.

Heisenberg talks about objections to Pauli's argument as regards the proof of the unitary character of the S-matrix.