Campkin, Ben (2013): . I.B.Tauris. ISBN 978-0-857-73416-7. Christopher, John (2013): . Amberley Publishing Limited. ISBN 978-1-445-62359-7. Day, John R.; Reed, John (2008): , 10. utg., første gang utgitt 1963. Capital Transport. ISBN 978-1-85414-316-7. Gourvish, Terry; Anson, Mike (2004): . Oxford University Press. ISBN 978-0-19926-909-9.