Bower, R. G., Lucey, J., & Ellis, R. S. (1992). Precision photometry of early-type galaxies in the Coma and Virgo clusters: a test of the universality of the colour–magnitude relation – I. The data. Monthly Notices of the Royal Astronomical Society, 254(4), 589-613. https://doi.org/10.1093/mnras/254.4.589