TRUST - I. A 3D externally illuminated slab benchmark for dust radiative transfer K. D. Gordon, M. Baes, S. Bianchi, P. Camps, M. Juvela, R. Kuiper, T. Lunttila, K. A. Misselt, G. Natale, T. Robitaille and J. Steinacker A&A, 603 (2017) A114 Published online: 19 July 2017 DOI: 10.1051/0004-6361/201629976