Pauli agrees with Källén about the correctness of the mathematics of the Lee-model. He writes on a question where to publish the paper. He agrees with Källén that Heisenberg's idea about the derivation of the electromagnetic field from spinor-fields must be wrong. He hopes that an improved renormalization mathematics might lead to a sort of eigenvalue-problem for the fine-structure constant.

Pauli writes on the criticism of a calculation by Mr Kurepa.

Pauli questions if there are other models beside Lee's model for renormalization. He describes a model by Thirring which avoids negative probabilities and which allows a transition to the limit of relativistic mesons.

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.