1. W3C. (2004a). OWL Web ontology language reference. Retrieved August 20, 2009, from http://www.w3.org/TR/2004/REC-owl-ref-20040210/.
2. W3C. (2004b). SWRL: A semantic Web rule language combining OWL and RuleML. Retrieved August 20, 2009, from http://www.w3.org/Submission/SWRL.
3. ALEKS Corporation. (2008). ALEKS teacher’s menu for K-12 (Version 3.8). Retrieved August 20, 2009, from http://www.aleks.com/k12/user_guides
4. ALEKS Corporation. (2009). ALEKS Corporation Web site. Retrieved August 20, 2009, http://www.aleks.com
5. A multi-agent infrastructure for developing personalized web-based systems