?url_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.aulast=Liu&rft.aufirst=XW&rft.au=Liu%2C+XW&rft.issn=0035-8711&rft.date=October+2001&rft.volume=327&rft.issue=1&rft.atitle=Chemical+abundances+of+planetary+nebulae+from+optical+recombination+lines+-+III.+The+Galactic+bulge+PN+M+1-42+and+M+2-36&rft.title=Monthly+Notices+of+the+Royal+Astronomical+Society&rft.pages=141-168&rft.genre=article