Dirk Frosch-Wilke Salvador Sánchez Alonso Juan Manuel Dodero Evolutionary Design of Collaborative Learning Processes through Reflective Petri Nets. 423-427 2008 ICALT http://dx.doi.org/10.1109/ICALT.2008.70 conf/icalt/2008 db/conf/icalt/icalt2008.html#Frosch-WilkeAD08