Nickelson, L., T. Gric, S. Asmontas, and R. Martavicius. 2008. “Electrodynamical Analyses of Dielectric and Metamaterial Hollow-Core CylindricalWaveguides”. Elektronika Ir Elektrotechnika 82 (2): 3-8. https://doi.org/10.5755/j02.eie.11043.