McClintock, Robert
Houghton Mifflin, 1967
Buku Teks
Osgood, Robert Endicott
Westview Press, 1979
Buku Teks
Gray, Colin S., author
Routledge, 2012
Buku Teks
edited by John J. McIntyre
National Defense University Press, 1979
Buku Teks
Frederick A. Praeger, 1962
Buku Teks