Soltau, Roger H.
Longmans, Green , 1960
Buku Teks
Barnes, James F.
St. Martin`s Press, 1980
Buku Teks
Laski, Harold J.
George Allen and Unwin, 1960
Buku Teks
Laski, Harold J.
MCML Yayasan Pembangunan, 1950
Buku Teks
Marcos, E.Ferdinand
The Marcos Foundation, 1978
Buku Teks