@misc {IOPORT.70642426,
    author       = {Baghaei, Nilufar and Mitrovic, Antonija},
    title        = {Evaluating a collaborative constraint-based tutor for UML class diagrams},
    howpublished = {AIED, 533-535 (2007).},
    year         = {2007},
    identifier   = {70642426},
}