Actually when I was at university only a couple of years ago it became perfectly allowable to reference Wikipedia in research projects and essays. Wikipedia is well structured, categorised, referenced and resourced. It's main articles are very factual, and you can usually tell how reliable an article is by how many references it has. Wikipedia's 9/11 page has almost 300 individual references, with several dozen other Wiki pages coming off it with equally good sourcing. It is factual, and complete the vast majority of the time. Only people kidding themselves say otherwise.
It is sad to learn that our Universities are this dumbed down. Research papers should contain source documents.
Wikipedia: check the sources in the article to verify authenticity. - - - Updated - - - He's not American.