Rebecca Armstrong, Rhodri Marsden, Abigail Outhwaite and Jimmy Lee Shreeve (11 June 2007). 101 Really Useful Websites (页面存档备份,存于互联网档案馆), The Independent. Retrieved 15 May 2011.
Rebecca Armstrong, Rhodri Marsden, Abigail Outhwaite and Jimmy Lee Shreeve (11 June 2007). 101 Really Useful Websites (页面存档备份,存于互联网档案馆), The Independent. Retrieved 15 May 2011.