Nitrogen isotope fractionation in protoplanetary disks Ruud Visser, Simon Bruderer, Paolo Cazzoletti, Stefano Facchini, Alan N. Heays and Ewine F. van Dishoeck A&A, 615 (2018) A75 Published online: 17 July 2018 DOI: 10.1051/0004-6361/201731898