A. M. Shutovskyi, A. V. Svidzinskyi, V. E. Sakhnyuk, and O. Y. Pastukh, “Microscopic Calculation of Josephson Current in Tunnel Junctions with Two-Gap Superconductors”, Ukr. J. Phys., vol. 63, no. 11, p. 1001, Dec. 2018.