Pauli acknowledges letter Heisenberg's of 5 and 6 March and a new manuscript. He makes critical comments on this new version. He writes of Landeau's interest in their theory.

Pauli cannot agree to Heisenberg's optimism in his letter of 26 March and maintains his criticism expressed in the letter of 25 March.

Pauli acknowledges receipt of Heisenberg's Planck lecture.

Pauli replies to Heisenberg's question in his letter of 5 October.

Pauli questions and comments on the theory of holes.

Pauli writes about the difficulties of the theory of holes, as far as physical interpretation is concerned.

Pauli gives further critical comments on Heisenberg's formalism. He writes of Bloch's report on a theory of Beta-desintegration by Fermi.

Pauli talks about the solution he found for the matrix problem.

In connection with a note by De Broglie, published in: comptes rendus: (1934) Bd. 198, Heft Nr. 2, S. 135, Pauliremarks that the main problem is the correct formulation of the interaction terms of neutrino and electrons.

Appendix to the letter of the same date, entitled: "Ueber die quanten-elektrodynamische Formulierung der Löcher-theorie".