Millimetre spectral indices of transition disks and their relation to the cavity radius P. Pinilla, M. Benisty, T. Birnstiel, L. Ricci, A. Isella, A. Natta, C. P. Dullemond, L. H. Quiroga-Nuñez, T. Henning and L. Testi A&A, 564 (2014) A51 Published online: 03 April 2014 DOI: 10.1051/0004-6361/201323322