Sagarin, Rafe, author
Island Press, 2012
eBooks
Caper, Robert, author
Routledge, Taylor & Francis Group, 2009
Buku Teks
Allwright, Dick, author
Longman, 1993
Buku Teks
Podmore, Valerie N. , author
McGraw-Hill, 2012
Buku Teks
edited by George J. McCall, J.L. Simmons.
Random House, 1969
Buku Teks