Extra-planar H I in the starburst galaxy NGC 253 R. Boomsma, T. A. Oosterloo, F. Fraternali, J. M. van der Hulst and R. Sancisi A&A, 431 1 (2005) 65-72 Published online: 02 February 2005 DOI: 10.1051/0004-6361:20041715