Mohamed Quafafou Moussa Boussouf Generalized rough sets based feature selection. 3-17 2000 4 Intell. Data Anal. 1 http://iospress.metapress.com/openurl.asp?genre=article&issn=1088-467X&volume=4&issue=1&spage=3 db/journals/ida/ida4.html#QuafafouB00