Moskalenko, V., Dohotaru, L., Digor, D., & Cebotari, I. (2012). Stationary property of the thermodynamic potential of the Hubbard model in strong coupling diagrammatic approach for superconducting state. ФІЗИКА НИЗЬКИХ ТЕМПЕРАТУР, 38(10), 1167–1174. https://doi.org/10.1063/1.4758767