Matthias Wiesmann André Schiper Beyond 1-Safety and 2-Safety for Replicated Databases: Group-Safety. 165-182 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=2992&spage=165 2004 conf/edbt/2004 EDBT db/conf/edbt/edbt2004.html#WiesmannS04