Pauli asks about stopping off at the Frankfurt institutes on his return trip from Göttingen.

Heisenberg writes about Pauli's remarks on a paper by Born and Heisenberg.

Heisenberg writes about the polarization of spectral lines in electric and magnetic fields according to quantum theory.

Heisenberg says that in his new mechanics, the geometrical concept of orbit has no sense, as orbits are not observables.

Heisenberg replies to Pauli and Källén, in particular about "Hilbert-space II". He makes some remarks on the physical contents of his mathematical formalism.

Heisenberg writes about the importance of his function $\chi$a(xx') for his quantized field theory.

Heisenberg replies to Pauli's question as regards the "Hilbert-space II" formalism, and the commutation relations on the light-cone. He also speculates about the importance of e$^{2}$/h.c.

Heisenberg attempts to justify his axiomatics and to show that it is less arbitrary than suspected by Pauli.