Van Kerkwijk, M.H.; Breton, R.P.; Kulkarni, S.R. (2011). «Evidence for a Massive Neutron Star from a Radial-Velocity Study of the Companion to the Black-Widow Pulsar Psr B1957+20». The Astrophysical Journal728 (2): 95. doi:10.1088/0004-637X/728/2/95. Bibcode: 2011ApJ...728...95V.
Van Kerkwijk, M.H.; Breton, R.P.; Kulkarni, S.R. (2011). «Evidence for a Massive Neutron Star from a Radial-Velocity Study of the Companion to the Black-Widow Pulsar Psr B1957+20». The Astrophysical Journal728 (2): 95. doi:10.1088/0004-637X/728/2/95. Bibcode: 2011ApJ...728...95V.