Bock, Edwin A.
London Prentice-Hall 1962
Buku Teks
Holsti, Ole R.
Boston Allen & Unwin 1984
Buku Teks
Baltimore : Johns Hopkins University Press
Majalah, Jurnal, Buletin
Griffith, Ernest S.
London Methuen & Co. 1967,
Buku Teks
Mathias, L.L.
Hamburg Rowohlt 1953
Buku Teks