Phillipa Oaks Arthur H. M. ter Hofstede David Edmond Murray Spork Extending Conceptual Models for Web Based Applications. 216-231 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=2813&spage=216 2003 conf/er/2003 ER db/conf/er/er2003.html#OaksHES03