Author Posting. (c) Taylor & Francis, 2007. This is the author's version of the work. It is posted here by permission of Taylor & Francis for personal use, not for redistribution. The definitive version was published in Numerical Functional Analysis and Optimization, Volume 28 Issue 7, July 2007.
doi:10.1080/01630560701493321 ( http://dx.doi.org/10.1080/01630560701493321 )