Pauli writes about a report from the USA by Jost that Bogoljubow has advanced more than anybody else in the mathematics of dispersion relations.

Pauli sends forms to be filled out for CERN.

Pauli encloses a letter by Heisenberg and asks Källén to write to him.

Pauli expresses his doubts whether Källén's mathematics has anything to do with physics. He talks about Heisenberg's approach to the problem of field theory.

Pauli talks about the progress made by Taylor in Princeton and Bogoljubov in dispersion relations and he writes about the article for the Springer Handbuch.

Pauli talks more about Springer and time-dependent wave-packets in a Lee model with complex roots. He writes on the interpretation of isotopic spin.

Pauli replies to Källén's solution in his letter of the 9 January 1958 with additional remarks about $\lambda_{o}$-particles, the identity of "isospace" with Hilbert-space and the fourfold degeneracy of the vacuum and its removal.

Pauli asks for Källén's opinion about Hurst's paper and quotes Thirring's comment.

Pauli comments on Källén's paper. There are differences between his part I and part II. He talks about states with one electron-positron pair and about Dyson's view that only renormalized interactions existing in nature.