Nightingale, J., Smith, R. J., He, Q., O’Riordan, C. M., Kegerreis, J. A., Amvrosiadis, A., Edge, A. C., Etherington, A., Hayes, R. G., Kelly, A., Lucey, J. R., & Massey, R. J. (2023). Abell 1201: detection of an ultramassive black hole in a strong gravitational lens. Monthly Notices of the Royal Astronomical Society, 521(3), 3298-3322. https://doi.org/10.1093/mnras/stad587