Simmonds, J.D.
Columbia University Press, 1970
Buku Teks SO
Kit, Lau
[Publisher not identified], [Date of publication not identified]
Buku Teks
edited by Ian Wilson
Angus and Robertson, 1973
Buku Teks SO
Hinton, Harold C.
Houghton Miffiln, 1966
Buku Teks SO
Barnett, Arthur Doak
Overseas Development Council, 1979
Buku Teks SO