1. Hannaford, C.D.: ‘The finite-difference method for waveguides’, 1967, University of Leeds, Department of Electrical & Electronic Engineering
2. Morse, P.M., and Feshback, H.: Methods of theoretical physics, (McGraw-Hill 1953),pt. 11
3. ‘Wave equations and variational formulation for generalised isotropic medium in wave-guides’, research report, LU/EE/68/01,