YI, D. Evaluation Research on the Circular Economy Efficiency of the Coal Industry Based on Dea Model. Journal of Mines, Metals and Fuels, [S. l.], v. 65, n. 9, p. 479–484, 2017. DOI: 10.18311/jmmf/2017/26974. Disponível em: http://informaticsjournals.com/index.php/jmmf/article/view/26974. Acesso em: 27 apr. 2024.