Jakarta : The Ambassador of The Republic of Zimbabwe, 2007,
Majalah, Jurnal, Buletin
Yudelman, Montague, author
Harvard University Press , 1975
Buku Teks
Council for Research in Values and Philosophy, 2008.
Buku Teks
Rayner, William, author
Frederick A. Praeger, 1962
Buku Teks
Faruqee, Rashid
World Bank , 1981
Buku Teks