Ioannis Hatzilygeroudis Christos Giannoulis Constantinos Koutsojannis A Web-Based Education System for Predicate Logic. 2004 conf/icalt/2004 ICALT db/conf/icalt/icalt2004.html#HatzilygeroudisGK04 http://dx.doi.org/10.1109/ICALT.2004.1357384 0-