Ridker, Ronald G.
Washinton The World Bank 1994,
Buku Teks
Yeh, Stephen H.K., author
UNESCO, 1990
Buku Teks
Byars, Llyod L., author
Richard D. Irwin, 1984
Buku Teks
edited by Gavin W. Jones and Terence H. Hull
Institute od Southeast Asia Studies (ISEAS), 1997
Buku Teks
Washington, D.C. The Bank 1981,
Buku Teks