Trapping dust particles in the outer regions of protoplanetary disks P. Pinilla, T. Birnstiel, L. Ricci, C. P. Dullemond, A. L. Uribe, L. Testi and A. Natta A&A, 538 (2012) A114 Published online: 10 February 2012 DOI: 10.1051/0004-6361/201118204