Journal article (2004) - PHJ Kouwer (author), W.F. Jager (author), Wolter Jager (author), Wolter F. Jager (author), WJ Mijs (author), S.J. Picken (author), Stephen Picken (author), SJ Picken (author), S. J. Picken (author), Stephen J. Picken (author), KJ Shepperson (author)