Routledge, 1998
Buku Teks
edited by Susie Beattie and Rachel Smith
Harper and Collins, 2011
Buku Referensi
HarperCollins, 2011
Buku Referensi
Wichman, Karl
Philadelphia, David McKay Company, 1944
Buku Referensi
Berlin Hodder and Stoughton 1966
Buku Referensi