Sircar, Muhammad Jamiruddin
Form International, 2003
Buku Teks SO
Gardner, Richard N.
Dell Publishing, 1965
Buku Teks SO
Packenham, Robert A
Princeton University Press, 1976
Buku Teks SO
Spykman, Nicholas John
York Harcourt Brace , 1942
Buku Teks
Whittaker, David J.
Routledge, 1997
Buku Teks SO