Whyte, Robert Orr, author
Westview Press, 1982
Buku Teks
Dixon, Ruth B., author
Published for Resources for the Future by the Johns Hopkins Press, 1978
Buku Teks
United Nations Development Programme, 1980
Buku Teks
Artikel Jurnal
Louise Edwards, Mina Roces, editor
Allen & Unwin , 2000
Buku Teks