The mass-metallicity relation of high-z type-2 active galactic nuclei K. Matsuoka, T. Nagao, A. Marconi, R. Maiolino, F. Mannucci, G. Cresci, K. Terao and H. Ikeda A&A, 616 (2018) L4 Published online: 14 August 2018 DOI: 10.1051/0004-6361/201833418