Groenendael, Victoria M. Clara van, author
Foris Publications, 1987
Buku Referensi
Freedman, Ronald, author
Irvington, 1975
Buku Teks
Clamp, Cynthia G. L., author
Sage, 1999
Buku Teks
International Development Research Centre, 1983
Buku Teks
Bridson, Gavin D.R.
Gerland Publishing, Inc., 1994
Buku Teks