J1721+8842: a gravitationally lensed binary quasar with a proximate damped Lyman-α absorber C. Lemon, M. Millon, D. Sluse, F. Courbin, M. Auger, J. H. H. Chan, E. Paic and A. Agnello A&A, 657 (2022) A113 Published online: 20 January 2022 DOI: 10.1051/0004-6361/202142138