Robertson, Christoper R.
London: Edward Arnold, 1993
Buku Teks
Haftman, Werner, author
Frederick A. Praeger, Pub., 1960
Buku Referensi
Rawson, K.J., author
Butterworth-Heinemann, 2001
Buku Teks
Cobban, Alfred, author
Braziller, 1965
Buku Teks
edited by Graeme Barker
Routledge, 1999
Buku Referensi