Andrzej Jankowski James F. Peters Andrzej Skowron Jaroslaw Stepaniuk Optimization in Discovery of Compound Granules. 249-265 2008 85 Fundam. Inform. 1-4 http://iospress.metapress.com/content/14347510p00p7w48/ db/journals/fuin/fuin85.html#JankowskiPSS08