Maurice van Keulen Jochem Vonk Arjen P. de Vries Jan Flokstra Henk Ernst Blok Moa and the Multi-model Architecture: A New Perspective on XNF 2. 67-76 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=2736&spage=67 2003 conf/dexa/2003 DEXA db/conf/dexa/dexa2003.html#KeulenVVFB03