Källén writes on an interim report on his work on quantum electrodynamics.

Källén criticizes Thirring's remarks about his theory communicated by Pauli.

Källén comments on the paper by Heisenberg and Haag. He writes on Wightman's axioms.

Källén has difficulties in understanding Pauli's last letter. He talks about rumours regarding the discovery of spin in $\Pi^{+}$-mesons.

Källén talks about Heisenberg's claim that the states in the Hilbert-space I possess a positive norm.

Källén writes on the results of his and Wightman's calculations on the properties of certain analytical functions.

Källén talks about his calculations on fields with indefinite metric.

Källén talks about a calculation in connection with his work on the Lee model.

Källén replies to Pauli's letter of the 2 February 1958 on the product of two or more field operators.

Källén talks about some calculations in connection with Lee's model.