Wilson, E. Bright, author
McGraw-Hill, 1952
Buku Teks
Freedman, Paul, author
Public Affairs Press, 1950
Buku Teks
Russell, Richard Joel, author
May, 1960
Buku Teks
Beach, David P., author
Prentice-Hall, 1992
Buku Referensi
Ford, E. David, author
Cambridge University Press, 2000
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