Hanson, James A., author
World Bank, 1992
Buku Teks
Robinson, Joan, author
Richard D. Irwin, 1956
Buku Teks
Keirstead, B. S. (Burton Seely), author
Basil Blackwell, 1959
Buku Teks
Rosovsky, Henry, author
Free Press, 1961
Buku Teks
Cairncross, A.K., author
Cambridge University Press, 1953
Buku Teks