?url_ver=Z39.88-2004&rft_id=10.1111%2Fj.1365-2966.2007.11492.x&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.au=McCallum%2C+JN&rft.aulast=McCallum&rft.aufirst=JN&rft.issue=2&rft.volume=376&rft.date=2007&rft.issn=0035-8711&rft.atitle=Magnetic+field+limits+and+spectral+variability+in+the+Circinus+galaxy+H2O+megamasers&rft.title=Monthly+Notices+of+the+Royal+Astronomical+Society&rft.pages=549-556&rft.genre=article