Multiple spiral patterns in the transitional disk of HD 100546 A. Boccaletti, E. Pantin, A.-M. Lagrange, J.-C. Augereau, H. Meheut and S. P. Quanz A&A, 560 (2013) A20 Published online: 29 November 2013 DOI: 10.1051/0004-6361/201322365