O’neill, S, Kiehlmann, S, Readhead, A C S, Aller, M F, Blandford, R D, Liodakis, I, Lister, M L, Mróz, P, O’dea, C P, Pearson, T J, Ravi, V, Vallisneri, M, Cleary, K A, Graham, M J, Grainge, K J B, Hodges, M W, Hovatta, T, Lähteenmäki, A, Lamb, J W, Lazio, T J W, Max-moerbeck, W, Pavlidou, V, Prince, T A, Reeves, R A, Tornikoski, M, Vergara De La Parra, P & Zensus, J A 2022, ' The Unanticipated Phenomenology of the Blazar PKS 2131–021: A Unique Supermassive Black Hole Binary Candidate ', The Astrophysical Journal Letters, vol. 926, no. 2, pp. L35 . https://doi.org/10.3847/2041-8213/ac504b