HST/ACS observations of shell galaxies: inner shells, shell colours and dust G. Sikkema, D. Carter, R. F. Peletier, M. Balcells, C. del Burgo and E. A. Valentijn A&A, 467 3 (2007) 1011-1024 Published online: 26 March 2007 DOI: 10.1051/0004-6361:20077078