V. Wiktor Marek Miroslaw Truszczynski Rough Sets - What Are They About? 24 1998 conf/rsctc/1998 Rough Sets and Current Trends in Computing http://link.springer.de/link/service/series/0558/bibs/1424/14240024.htm db/conf/rsctc/rsctc1998.html#MarekT98