José A. Cruz-Lemus Marcela Genero M. Esperanza Manso Mario Piattini Evaluating the Effect of Composite States on the Understandability of UML Statechart Diagrams. 113-125 2005 conf/uml/2005 MoDELS http://dx.doi.org/10.1007/11557432_9 db/conf/uml/models2005.html#Cruz-LemusGMP05