Falah, F., M. A. R. Lubis, T. Triastuti, W. Fatriasari, and F. P. Sari. “Utilization of Lignin from the Waste of Bioethanol Production As a Mortar Additive”. Jurnal Sylva Lestari, vol. 8, no. 3, Sept. 2020, pp. 326-39, doi:10.23960/jsl38326-339.