TY JOUR TI Assessment of the competitive environment and prospects for the development of the oil industry in Russia: current problems and possible solutions KW oil industry KW imperfect competition KW oligopoly KW concentration indices KW exports KW sanctions KW Herfindahl-Hirschman index KW dispersion of market shares JO Theoretical economics AU Varvus, S.A. AU Efremova, A.A. PY 2024 IS 0 PB Yaroslavl State Technical University