Pauli continues with his calculations with hyper-complex numbers. He adds some remarks on "neutretto"-scattering and the theory of mesons.

A short addendum to the last letter.

Pauli talks about reasons for writing to Klein and not to Bohr, involvement with Heisenberg in field theory, Heisenberg's "artificial" solution of the commutation problem, difficulty with continuous beta-decay energy, and shortcomings of the field theory.

Pauli congratulates Klein on his work, his new position and remarks on physics in Sweden and Klein's work. Pauli describes his attempts to treat beta decay using "neutron" hypothesis. Pauli gives arguments against failure of energy

Pauli talks about the question of Fermi-statistics for zero-spin particles.

Pauli writes about his travel plants to Stockholm for the Nobel Prize and he informs Klein of a paper by Heisenberg on superconductivity.

Pauli hopes that Klein will come to Zürich.

Pauli hopes that Klein will be present when he will the Pais' w-space.

Pauli asks about the Copenhagen Conference. He criticises the Heisenberg-Pauli papers, makes remarks on superconductivity and about Dirac's negative mass.

Addition to the last letter (17 July) about hermitic operators. Pauli talks about the five dimentional formalism.