Moshkun, I.; Boyd, T.J.M.; Newton, R.H.C.: 'Guided modes of a four-layer optical waveguide with a metal buffer', Electronics Letters, 1978, 14, (18), p. 587-588, DOI: 10.1049/el:19780393
IET Digital Library, https://digital-library.theiet.org/;jsessionid=7msk81ls0l7j9.x-iet-live-01content/journals/10.1049/el_19780393