1. O.N. Stavroudis, The Optics of Rays, Wavefronts, and Caustics. (Academic press, Cambridge, 1972)
2. O.N. Stavroudis, The mathematics of geometricl and physical optics. (Wiley, 2006)
3. A Pressley, Elementary Differential Geometry, The Springer Undergraduate Mathematics Series, (2001) p. 123
4. J.A. Hoffnagle, D.L. Shealy, Refracting the k-function: Stavroudis’s solution to the eikonal equation for multielement optical systems. J. Opt. Soc. Am. A 28, 1312–1321 (2011)
5. D.L. Shealy, D.G. Burkhard, Caustic surfaces and irradiance for reflection and refraction from an ellipsoid, elliptic parabolid and elliptic cone. Appl. Opt. 12, 2955–2959 (1973)