Masahiro Inuiguchi Generalizations of Rough Sets: From Crisp to Fuzzy Cases. 26-37 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=3066&spage=26 2004 conf/rsctc/2004 Rough Sets and Current Trends in Computing db/conf/rsctc/rsctc2004.html#Inuiguchi04