F. Rivera, Jhonathan, Johanna M. Mejia, Ruby Mejia de Gutierrez, and Marisol Gordillo. 2014. “Hybrid Cement Based on the Alkali Activation of by-Products of Coal”. Revista De La Construcción. Journal of Construction 13 (2):31-39. http://146.155.94.136/index.php/RDLC/article/view/13536.