Eppen, Gary D., author
Prentice Hall International, 1988
Buku Teks
Dagron, Alfonso Gumucio, author
The Rockefeller Foundation, 2001
Buku Teks
Gorlewski, Julie A.
Sense, 2012
eBooks
Buzan, Barry, author
Cambridge University Press , 2015
Buku Teks
Rickards, James, author
Portfolio/Penguin, 2011
Buku Teks