Källén writes about charge renormalization.

Källén talks about the difficulties of the indefinite metric in quantum electrodynamics.

Pauli makes more remarks about relativistic cosmology and references to Jordan's theory.

Lehmann makes some remarks about the meson theory and the work of Dyson and Dalitz connected with it.

Källén writes on further doubts as regards the Heisenberg model.

Källén talks about certain results of his calculations on singular functions important for the analyticity properties of the n-fold expectation value.