Erisman, H. Michael, author
Westview Press, 1985
Buku Teks
Department of State, 1961
Buku Teks
Saruski, Jaime
UNESCO, 1979
Buku Teks
International Bank for Reconstruction and Development ; editor, Francis Adams Truslow
John Hopkins Press, 1953
Buku Teks
Sage Publications, 1982
Buku Teks