Anna E. Bobkowska A Methodology of Visual Modeling Language Evaluation. 72-81 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=3381&spage=72 2005 conf/sofsem/2005 SOFSEM db/conf/sofsem/sofsem2005.html#Bobkowska05