Method of Approximation for the Meson-Nucleon Problem when the Interaction is Fixed and Extended

It is proposed that a consistent and satisfactory method for evaluating the fixed extended source meson problem is: (a) first to renormalize the calculation by the method of the preceding paper; (b) to evaluate the fundamental quantities $L_r$ and ${\Sigma }_r$ by the usual weak coupling method; (c) also to use standard perturbation theory for the irreducible diagrams except when poles occur in integrations over intermediate states. Sums of diagrams in which repeated poles occur should be evaluated exactly.