Current, Richard N., author
Alfred A. Knopf, 1965
Buku Teks
Eder, Phanor J., author
New York University press, 1950
Buku Teks
Eder, Phanor J., author
Oxford University Press, 1950
Buku Teks
Barger, Harold, author
Rand McNally, 1964
Buku Teks
Barger, Harold
Chicago: Rand McNally, 1964,
Buku Teks