Pauli awaits experiments on beta-decay "neutron" hypothesis. Pauli asks for an answer from Bohr to Pauli's arguments against failure of energy conservation in his letter of 12 Dec.

Reply from Pauli to letters by Klein, especially about five-dimensional formalism.

Pauli makes a comparison of Klein's theory with his relevant lecture given in Paris.

Pauli gives further details about the impending visit to Sweden.

Pauli writes about thermodynamical irreversibility and quantum theory. He makes remarks about Pais' work and his W-space, about quantum field theory and about the analogy between the electromagnetic eigen-field of an electron and the gravitational eigen-field of a photon.

Pauli gives his views on mutations and selection. He makes remarks on Klein's work and Heisenberg's attempts at a unified field theory. Pauli makes plans for a relativity congress.

Pauli asks for classification of Klein's work.

Pauli criticizes Klein's notation and a commutator relation. He refers him to Rosenfeld (1930).

Pauli reports his coming absence in case Klein's third draft arrives then.

Pauli writes about his plans for his visit to Sweden.