TY JOUR TI Value investing strategy in undervalued stocks of Russian companies KW value investing KW stock market KW undervalued stocks KW fundamental analysis KW investment attractiveness KW financial multipliers KW Graham number KW oil and gas sector KW metals KW mining industry KW power sector JO Theoretical economics AU Naryzhnaya, Y.V. AU Dubrova, T.V. AU Semyashkin, E.G. PY 2026 IS 0 PB Yaroslavl State Technical University