Wilson, E. Bright
McGraw-Hill, 1952
Buku Teks
Freedman, Paul
Public Affairs Press, 1950
Buku Teks
Beach, David P.
Prentice-Hall, 1992
Buku Referensi
Ford, E. David
Cambridge University Press, 2000
eBooks
E. David Ford
Cambridge University Press, 2000
eBooks