Tissue Preservation Index (TPI) and Gelification Index (GI) with the Quality of Coal as well as the Connection to the Acid Water MiningMuhammad Ilham Fatkhurrahman, Dian Agus Widiarso, Devina Trisnawati, Ahmad Zaki Romi and dan Arya GustiframE3S Web Conf., 202 (2020) 04005DOI: https://doi.org/10.1051/e3sconf/202020204005