Yes, the question's been asked once or twice! There is also a search function on pprune or you can use google to search pprune. I would also recommend that you just rowse the threads on this forum, just go back a couple of pages and you'll find a wealth of answers.
Oxford say this, Stapleford say that - basic psychology should tell you that there's an element of truth in each and an element of BS!
Cheers
Whirls