Helen C. Purchase Linda Colpoys Matthew McGill David A. Carrington UML Collaboration Diagram Syntax: An Empirical Study of Comprehension. 13-22 2002 conf/vissoft/2002 VISSOFT http://doi.ieeecomputersociety.org/10.1109/VISSOF.2002.1019790 db/conf/vissoft/vissoft2002.html#PurchaseCMC02