edited by Richard P. Stebbins
American Book-stratford Press, 1963
Buku Teks
Sutter, Robert G, author
Lanham Rowan & Littlefield, 2016
Buku Teks
Brown, Seyom, author
Brookings institution Press, 2003
Buku Teks
edited by Raymond Dennett
World Peace Foundation, 1950
Buku Teks
Spanier, John
Frederck A. Praeger, 1968
Buku Teks