KRAWIEC, M. Efficiency of indirect ways of investing in commodities in conditions of polish capital market. Metody Ilościowe w Badaniach Ekonomicznych, [S. l.], v. 12, n. 1, p. 105–118, 2011. Disponível em: https://qme.sggw.edu.pl/article/view/3101. Acesso em: 9 maj. 2024.