The singular eigenfunction method for solving transport equations introduced by K. M. Case in 19601has become extremely popular, at least in some circles, because of its close analogy to the classical method of treating partial differential equations, i.e. eigenfunction expansions. Because of a perceived lack of rigor in Case's work, alternate methods were developed later which were supposed to retain most of the advantage that Case's method had over classical Fourier transform methods (Wiener-Hopfl—i.e., elegance—while dispensing with Case's heuristic arguments. These methods were the resolvent integration technique of Larsen-Habetler2and the Hilbert space approach of Rutger Hansel broek3