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
Habson, 1986
Buku Teks
Parkinson, Joy, author
Churchill Livingstone, 2004
Buku Teks