Key points are not available for this paper at this time.
Analytic solutions are found for skew ray paths in inhomogeneous cylindrical systems such as GRIN rods and gas lenses, which focus rays by virtue of a gradual radial decrease in refractive index. The solutions are obtained by employing digital computers to carry out analytic, as opposed to numerical, calculations.
Paxton et al. (Sat,) studied this question.