2013:

      ​Cathryn M. Trott, Steven J. Tingay, Randall B. Wayth, The Astrophysical Journal Letters, Volume 776, Issue 1, pp. 6, (2013).

      D. Thornton, B. Stappers, M. Bailes et al., Science, Vol. 341, Issue 6141, pp. 53-56, (2013).