Heisenberg writes in clarification of an error in his calculation concerning the operator xa (xx').

Heisenberg replies to Pauli's letter and detailed discussion of Källén's arguments concerning Heisenberg's quantum field theory.

Heisenberg writes about two additions to his last letter, on a certain spinor and on the conditions for the finiteness of certain operators.

Heisenberg talks about calculations to prove the vanishing of the transitions to dipole ghost states by a limiting process, starting from the Lee model.

Heisenberg replies to critical comments by Pauli.

Heisenberg asks Pauli's opinion about the model by Cooper and Deser, and about the possibility of formulating a renormalized theory which contains only finite operators.

Heisenberg writes on two limits, defined by a maximal- and a minimal-condition, within which a theory of elementary particles is possible.

Heisenberg has some considerations proving the near relation between his work and the Lee-model.

Heisenberg makes a tentative reply to Pauli's question about dipole ghosts.

Heisenberg talks about objections to Pauli's argument as regards the proof of the unitary character of the S-matrix.