Pauli letter collection: letter to Gregor Wentzel

Pauli comments on papers by Wentzel and Fierz published in the Helv. Phys. Acta. He writes about the difficulties of all theories on nuclear forces. He writes about the anisotropy of neutron-proton scattering for higher energies, and its consequences for the theory. He comments on his paper on the Lambda-limiting process. He writes about Dirac's theory of photons with negative energy. He writes about the discovery of a new positive particle.