Pauli replies to Källén's letter of the 20 June 1955 and makes some mathematical comments. He talks about the Pisa conference.

Pauli replies to Källén's criticism of Thirring. He makes some remark about jealousy among colleagues. He writes on quotation from a paper by Landau (Bohr-Festschrift) about an argument of Pomeranchuk in favour of the absence of physical interactions for point particles. Note by Thirring on coupling of a spinor field with a scalar field and discussion of it.

Pauli is glad that the problem of the vacuum expectation value of the product of three field operators has been further clarified. He talks about Beta decay. He is convinced that reflexion invariance prevails in nature against of Lee, Yang and Salam.

Addition to the last letter about Heisenberg's calculations.

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

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 talks about his plans for a journey to England and Copenhagen. He writes more about parity violation.

Pauli refers to a paper by Heisenberg and explains a passage which was misinterpreted by Källén.

Pauli writes about another mathematical comment on Heisenberg's paper.

Pauli encloses a letter to Springer. He talks about a new paper by Schwinger on elementary particles. He writes on the logical connection of Källén's recent results to an example given by Jost last spring. He also talks about Thirring's model.