Nugent William R., author
Thomson Learning, 2001
Buku Teks
Paul J. Gertler, Sebastian Martines, Patrick Premand, Laura B. Rawlings, Christel M.J. Vermersch
World Bank, 2011
Buku Teks
Posavac, Emil J.
Prentice Hall Inc., 1980
Buku Teks
Grinnell, Richard M., author
Oxford University Press, 2018
Buku Teks
Patton, Michael Quinn, author
SAGE, 2015
Buku Teks