United Nations , 1987
Buku Teks
Verbit, Gilbert P.
Columbia University Press, 1969
Buku Teks
Hilling, David, author
Routledge, 1996
Buku Teks
King, Felicity Savage, author
Oxford University Press, 1995
Buku Teks
edited by Richard M. Bird and Oliver Oldman
John Hopkins, 1967
Buku Teks