Millist W. Vincent Michael Schrefl Jixue Liu Chengfei Liu Solen Dogen Generalized Inclusion Dependencies in XML. 224-233 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=3007&spage=224 2004 conf/apweb/2004 APWeb db/conf/apweb/apweb2004.html#VincentSLLD04