Extraction and Chemical Characterization of Humic Acid from Nitric Acid Treated Lignite and Bituminous Coal Samples.Published in:Sustainability (2071-1050), 2021, v. 13, n. 16, p. 8969, doi. 10.3390/su13168969By:Fatima, Noureen;Jamal, Asif;Huang, Zaixing;Liaquat, Rabia;Ahmad, Bashir;Haider, Rizwan;Ali, Muhammad Ishtiaq;Shoukat, Tayyba;ALOthman, Zeid A.;Ouladsmane, Mohamed;Ali, Tariq;Ali, Shafqat;Akhtar, Naseem;Sillanpää, MikaPublication type:Article