?url_ver=Z39.88-2004&rft_id=10.1051%2Fmatecconf%2F201710301004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.aulast=Yahya&rft.au=Yahya%2C+A.A.&rft.aufirst=A.A.&rft.title=Reducing+Heavy+Metal+Element+from+Coal+Bottom+Ash+by+Using+Citric+Acid+Leaching+Treatment&rft.date=2017&rft.issn=2261236X&rft.genre=proceeding