Cowen, Zelman, author
Oxford University Press, 1959
Buku Teks
Healey, Bede, author
Georgian House, 1972
Buku Teks
Longman Chesire, 1988
Buku Teks
Sinaga, Romawaty, author
Fakultas Ilmu Sosial dan Ilmu Politik Universitas Indonesia, 1998
UI - Skripsi (Membership)
Mathews, R.L. (Russell Lloyd), 1921-2000, author
Thomas Nelson, 1972
Buku Teks