Philipp Kostuch Krzysztof Socha Hardness Prediction for the University Course Timetabling Problem. 135-144 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=3004&spage=135 2004 conf/evoW/2004cop EvoCOP db/conf/evoW/evocop2004.html#KostuchS04