Staig, Robert Arnot., author
The University press,, 1931
Buku Teks
edited by Mark A. Jervis
Springer, 2005
Buku Teks
edited by Frederick W. Stehr
Kendall/Hunt, 1991
Buku Teks
Berenbaum, May R., author
Addison-Wesley, 1995
Buku Teks
editors, Tim Halliday, Kraig Adler, Christopher O'toole
Grolier International, 1993
Buku Referensi