Agüeros, M. A., Anderson, S. F., Margon, B., Posselt, B., Haberl, F., Voges, W., et al. (2006). Candidate isolated neutron stars and other optically blank X-ray fields identifier from the ROSAT all-sky and sloan digital sky surveys. Astronomical Journal, 131(3), 1740-1749. doi:10.1086/500049.