Swift XRT Observations of the Possible Dark Galaxy VIRGOHI 21DOI: info:10.1086/592819v. 686IOP PublishingL71–L74
Bonamente, Massimiliano, Swartz, Douglas A., Weisskopf, Martin C., and Murray, Stephen S. 2008. "Swift XRT Observations of the Possible Dark Galaxy VIRGOHI 21." The Astrophysical Journal Letters, 686 L71–L74. https://doi.org/10.1086/592819.