The nuclear ring in the unbarred galaxy NGC 278: Result of a minor merger? J. H. Knapen, L. F. Whyte, W. J. G. de Blok and J. M. van der Hulst A&A, 423 2 (2004) 481-493 Published online: 06 August 2004 DOI: 10.1051/0004-6361:20034336