The optically elusive, changing-look active nucleus in NGC 4156 Giulia Tozzi, Elisabeta Lusso, Lapo Casetti, Marco Romoli, Gloria Andreuzzi, Isabel Montoya Arroyave, Emanuele Nardini, Giovanni Cresci, Riccardo Middei, Silvia Bertolini et al. (14 more) A&A, 667 (2022) L12 Published online: 18 November 2022 DOI: 10.1051/0004-6361/202244987