Creighton, Donald, author
Macmillan, 1974
Buku Teks
Roskin, Michael G., 1939-, author
Pearson Education, 2015
Buku Teks
Wheare, K. C.
Oxford University Press, 1963
Buku Teks
Hauss, Charles, author
Wadsworth, 2009
Buku Teks
Hauss, Charles, author
Wadsworth and Cengage Learning, 2013
Buku Teks