Wikipedia

This is an authoritative and free open source encyclopedia. Independent reviews have revealed that it is as authoritative as longer established more expensive encyclopedias. However, the open source nature of this resource does mean that it should be used with caution. The facility to discuss more contentious contributions and the opportunity to review articles as they evolve makes this an interesting and important resource. Advice in how to cite contributions is provided and should be helpful to students. Wikipedia should not be the main source of literature in theses and dissertations!