?url_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.au=Gao%2C+DZ&rft.aufirst=DZ&rft.aulast=Gao&rft.issn=1936-0851&rft.title=ACS+NANO&rft.pages=5339+-+5351&rft.date=May+2014&rft.issue=5&rft.atitle=Using+Metallic+Noncontact+Atomic+Force+Microscope+Tips+for+Imaging+Insulators+and+Polar+Molecules%3A+Tip+Characterization+and+Imaging+Mechanisms&rft.volume=8&rft.genre=article