?url_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.aufirst=W.E.&rft.au=Ibrahim%2C+W.E.&rft.aulast=Ibrahim&rft.date=2018&rft.title=Petroleum+and+Coal&rft.atitle=Lithological+variations+in+black+shales+and+mudstone+formations+of+central+Sarawak%2C+Malaysia&rft.pages=446-452&rft.issue=3&rft.volume=60&rft.issn=13377027&rft.genre=article