Auguściuk, Elżbieta, and Grzegorz Biniecki. “Investigation of Parameters of the Multimode Four-Layer Waveguide Structures and Their Influence on the Light Propagation”. Photonics Letters of Poland, vol. 1, no. 3, Sept. 2009, pp. pp. 124-126, doi:10.4302/photon. lett. pl.v1i3.47.