Cohl & Tohline (1999) have shown how the integration/summation expression f
or the Green's function in cylindrical coordinates can be written as an azi
muthal Fourier series expansion, with toroidal functions as expansion coeff
icients. In this paper, we show how this compact representation can be exte
nded to other rotationally invariant coordinate systems which are known to
admit separable solutions for Laplace's equation.