Petr Husek Renata Pytelková System Modelling Using Fuzzy Numbers. 4921-499 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=2715&spage=4921 2003 conf/ifsa/2003 IFSA db/conf/ifsa/ifsa2003.html#HusekP03