Spacapan, Igor, and Miroslav Premrov. “Modal Analysis of Wave Motion in Inhomogeneous Waveguides Which Are Modelled by FEM”. Computer Assisted Methods in Engineering and Science 11, no. 2-3 (September 30, 2004): 137–144. Accessed May 8, 2026. http://cames.ippt.gov.pl/index.php/cames/article/view/1030.