KazankoО., PenkinaО., Butenko, V. and Holovko, O. 2024. Research and determination of the 1st and 2nd derivatives of the component terms of the dispersion equation for a flat two-layer one-dimensional periodic photonic crystal. Visnyk of V.N. Karazin Kharkiv National University, series “Radio Physics and Electronics”. 40 (Jun. 2024), 29-41. DOI:https://doi.org/10.26565/2311-0872-2024-40-03.