Harahap, Bhakti Hamonangan, et al. “Genesis of Pb-Zn-Cu-Ag Deposits Within Permian Carboniferous-Carbonate Rocks in Madina Regency, North Sumatra”. Indonesian Journal on Geoscience, vol. 2, no. 3, Nov. 2015, pp. 167-84, doi:10.17014/ijog.2.3.167-184.