When you are citing Wikipedia as a reference one thing you need to be aware of is that it is always changing. It would be unfortunate if you quoted something from it, and later someone checked your reference and the quote had been edited out.
What would be ideal is if they offered a “permalink” to a specific (current) revision accessible via the main article page. Until they do that you can get a permanent (or I assume p) link to a past revision from the history page.
This takes you to the latest revision:
This takes you to the revision as of 07:35, 8 Jul 2004
(Link was originally http://en.wikipedia.org/w/wiki.phtml?title=Dyson_sphere&oldid=4515898 but I shortened it. The link is obtainable from the history page)
Right bellow the article title it indicates that it is a revision as of a specific date. Ideally it should offer an obvious link to the most recent revision, maybe with the option to see the differences.