Källén writes to Pauli from CERN and gives the results of his calculations on the probabilities of dipole states.

Källén replies to Pauli about his difficulties as regards the S-matrix.

Källén writes of the result of his calculation of the splitting of a dipole state in the presence of an additional N-particle.

Källén writes from CERN on the discontinuous character of the S-matrix for the transition to the dipole ghost.

Glaser writes of his attempts to overcome the difficulty of "ghosts" in quantum electrodynamic field theory.

Glaser writes about the papers scheduled for the impending conference in CERN.