Boolean Basics
http://www.brightplanet.com/deepcontent/tutorials/search/part4.asp
Disney Online – Boolean Basics
http://family.go.com/raisingkids/learn/school/feature/famf0500websavi/famf0500websavi3.html
Boolean Tutorial
http://florin.syr.edu/webarch/searchpro/boolean_tutorial.html
Graphics from: GraphicGarden.com