Pratt, Julius W., author
Prentice-Hall, 1965
Buku Teks
Brookings institution, 1949
Buku Teks
Haviland, H. Field, author
The Brooking Institution, 1960
Buku Teks
Brokings Institution, 1950
Buku Teks
Hartmann, Frederick H., author
Macmillan, 1985
Buku Teks