HI holes and high-velocity clouds in the spiral galaxy NGC 6946 R. Boomsma, T. A. Oosterloo, F. Fraternali, J. M. van der Hulst and R. Sancisi A&A, 490 2 (2008) 555-570 Published online: 23 July 2008 DOI: 10.1051/0004-6361:200810120