Dixon, Chris J., author
Routledge, 2015
Buku Teks
Handelman, Howard, author
Pearson/Prentice Hall, 2006
Buku Teks
Mathur, Hari Mohan, author
Sage, 1986
Buku Teks
Todaro, Michael P., author
Longman, 1992
Buku Teks
edited by P. Ebow Bondzi-Simpson
Praeger, 1992
Buku Teks