1. Negative metric and the unitarity of the S-matrix
2. T. D. Lee: CERN preprint TH. 940(1969).
3. V. Glaser: private communication. Pauli and Glaser had discussed the problem from quite a different point of view than that adopted in the present paper; leaving completely arbitrary the classical field and using the conventional rules of computation, they had tried to find initial conditions to be imposed on the state function in such a way that the unitarity could be preserved asymptotically. But they have proved that these initial conditions were depending on the classical field, and this fact was judged unacceptable from the physical point of view.
4. Field and Charge Measurements in Quantum Electrodynamics