Caldwell, Wallace Everett, author
Holt, Rinehrt and Winston, 1963
Buku Teks
Matthews, Rupert, author
Miles Kelly, 2007
Buku Teks
edited by. Richard Garnett
Delhi, India Akashdeep 1992
Buku Referensi
Bulling, A.
E.J. Brill, , 1952.
Buku Teks
United Nations, 1978
Buku Teks