Retrieved June 19, 2003 from http://www.cheaptickets.com.
Expedia.
Retrieved June 19, 2003 from http://www.expedia.com
Harcourt School Publishers.
Retrieved June 22, 2003 from http://www.harcourtschool.com/newabreak/images/plane.jpg.
Mapquest.
Retrieved June 19, 2003 from http://www.mapquest.com.
Orbitz.
Retrieved June 19, 2003 from http://www.orbitz.com.
Travelocity.
Retrieved June 19, 2003 from http://www.travelocity.com.