CN rings in full protoplanetary disks around young stars as probes of disk structure P. Cazzoletti, E. F. van Dishoeck, R. Visser, S. Facchini and S. Bruderer A&A, 609 (2018) A93 Published online: 18 January 2018 DOI: 10.1051/0004-6361/201731457