“…In the formulation used by Luneburg and Hurd [9], there is a strip -Im ,/kz -(~~/ 1 6 a~) < Im w < Im ,/k2 -(n2/16a2) (which they do not mention). That is, their Green's function C(x, y; x', y') now has a bilateral Fourier transform analytic in the above strip, whereas the unilateral [9] should be replaced by a path P which is a line parallel to the real axis of the w plane, drawn in the strip which we have described here.…”