Ugwu, E. “Theoretical Study of Field Propagation Through a Nonhomogeneous Thin Film Medium Using Lippmann-Schwinger Equation”. The International Journal of Multiphysics 4, no. 4 (December 31, 2010): 305-316. Accessed August 10, 2022. http://journal.multiphysics.org/index.php/IJM/article/view/4-4-305.