edited by Ernest W. Lefever
Frederick A. Praeger, 1962
Buku Teks
Bechhoefer, Bernhard G., author
Brookings Institution, 1961
Buku Teks
edited by P. Edward Haley, David M. Keithly, and Jack Merritt
Westview Press, 1985
Buku Teks
Edward, David V., author
Holt, Rinehart and Winston, 1969
Buku Teks
Richard Dean Burns, editor in chief
Charles Scribner's Sons, 1993
Buku Referensi