edited by Kenneth Lee, Anne Mills
Oxford University Press, 1984
Buku Teks
Matherson, Ross, author
John Wiley & Sons, 1978
Buku Teks
Gelfand, M.A., author
Unesco, 1971
Buku Teks
edited by William R. Cline and Sidney Weintraub
Washington, D.C. , Brooklins Institution
Buku Teks
Braverman, Avishay, author
World Bank, 1989
Buku Teks