1. D. McGuinness and F van Harmelen (eds) OWL Web Ontology Language Overview http://www.w3.org/TR/2003/WD-owl-features-20030331/
2. M. Dean, G. Schreiber (eds), E. van Harmelen, J. Hendler, I. Horrocks, D. McGuinness, P. Patel-Schneider, L. Stein, OWL Web Ontology Language Reference http://www.w3.org/TR/2003/WD-owl-ref-20030331/
3. M. Smith, C. Welty, D. McGuinness, OWL Web Ontology Language Guide http://www.w3.org/TR/2003/WD-owl-guide-20030331/
4. P. Patel-Schneider, P. Hayes, I. Horrocks, OWL Web Ontology Language Semantics and Abstract Syntax http://www.w3.org/TR/2003/WD-owl-semantics-20030331/
5. J. Hefflin, Web Ontology Language (OWL) Use Cases and Requirements http://www.w3.org/TR/2003/WD-webont-req-20030331/