Hajiyev, N., M. Mansura, E. Sverdlikova, R. Safronov, and T. Vityutina. “Oligopoly Trends in Energy Markets: Causes, Crisis of Competition, and Sectoral Development Strategies”. International Journal of Energy Economics and Policy, vol. 11, no. 6, Nov. 2021, pp. 392-00, https://econjournals.com/index.php/ijeep/article/view/11634.