1. Kravtsov, Yu. A., Orlov, Yu. I.,Geometrical Optics of Inhomogeneous Media, Berlin: Springer-Verlag. 1990, 1–200.
2. Guo Hong, Deng Ximing, Differential geometrical methods in the study of optical transmission (scalar theory), I. Static transmission case,J. Opt. Soc. Am., 1995, A12(3):600.
3. Guo Hong, Deng Ximing, Differential geometrical methods in the study of optical transmission (scalar theory), II. Time-dependent transmission theory,J. Opt. Soc. Am., 1995, A12(3):607.
4. Deng Ximing,Dynamics of Light With Finite Beam Width (in Chinese), Hangzhou: Hangzhou University Press, 1993, 3–4.
5. Deng Ximing, Guo Hong, Cao Qing. The invariant integral and statistical equations of paraxial light beam transmission in free space,Science in China, Ser. A. 1997. 40(5):546.