Pauli discusses "Part IV" of Heisenberg's S-matrix theory published in: Zeitschrift für Naturforschung: 1, 608.

Pauli thanks Hulthén for sending the French edition of Lagervist's work on the Lamb shift.

Pauli writes of the preparations for his trip to Europe and of Schein's artificial meson production reported at the New York meeting.

Pauli discusses Schwinger's modification, published in: Physical review: (1942), 61, 387, of the Rosenfeld-Moller meson exchange theory. He obtains equations for deuteron ground state and discusses the attempts to solve them, with applications to scattering and work in

Pauli invites Hulthén to contribute to the Bohr issue, published in: Review of Modern Physics: (1945), Vol. 17.

Pauli reports on the stops during his journey to Zurich, Powell's doubts about Amaldi's results, problems of Wentzel and Villars with "strong coupling theory", and Dirac's latest views. He criticizes Gustafson's work, Peng's removal of divergences in meson theory and Heisenberg's S-matrix theory.

Pauli discusses the implication of forward neutron scattering for meson theory. He describes the attempt to obtain relativistic theory of deuteron quadrupole moment, and reports on his trip to Harvard.

Pauli discusses about Ning Hu's difficulties applying the relativistic Rosenfeld-Moller theory, the work of Wentzel and Lopes on "strong coupling" as explanation of Amaldi's results, and the war-time fates of Casimir, Kahn and Amaldi.

Pauli writes about mathematical contributions to the quantum-mechanical calculus.

Pauli discusses the question of a degenerated gas and compares statistics of Bose-Einstein with that of Fermi-Dirac. Another part of the letter deals with scattering which Pauli does not yet understand.