Eisenreich, M., Naab, T., Choi, E., Ostriker, J. P., & Emsellem, E. (2017). Active galactic nuclei feedback, quiescence and circumgalactic medium metal enrichment in early-type galaxies. Monthly Notices of the Royal Astronomical Society, 468(1), 751-768. doi:10.1093/mnras/stx473.