Parkinson, Joy, author
Churchill Livingstone, 2004
Buku Teks
Dixson, Robert J., author
Regents Oublishing, 1953
Buku Teks
Smith, John W. T., author
International Thomson, 1994
Buku Teks
Cambridge Hobsons 1987
Buku Referensi
Muinzer, Genevieve, author
Routledge and Kegan Paul, 1987
Buku Teks