?url_ver=Z39.88-2004&rft_id=10.1016%2Fj.egypro.2019.01.511&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.aufirst=S.W.Y.&rft.aulast=Cheng&rft.au=Cheng%2C+S.W.Y.&rft.issn=18766102&rft.title=The+effect+of+triangular+protrusions+on+geothermal+wellbore+heat+exchanger+from+retrofitted+abandoned+oil+wells&rft.date=2019&rft.genre=proceeding