1. CPN Tools website, http://cpntools.org/ (accessed: March 30, 2012)
2. Gecode website, http://www.gecode.org/ (accessed: March 30, 2012)
3. GreatSPN website, http://www.di.unito.it/~greatspn/index.html (accessed: March 30, 2012)
4. MC2 website, http://www.brc.dcs.gla.ac.uk/software/mc2 (accessed: March 30, 2012)
5. OGDF - Open graph drawing framework website, http://www.ogdf.net/doku.php/start (accessed: March 30, 2012)