Kemmerer, Donald L., author
Littlefield, Adams, 1956
Buku Teks
Williams, T. Harry, author
Alfred A. Knopf, 1963
Buku Teks
Rae, John B., author
Mc Graw-Hill Book Company, 1949
Buku Teks
Bemis, Samuel Flagg, 1891-1973, author
Holt, Rinehart and Winston, 1965
Buku Teks
Beard, Charles A., author
New Home Library, 1944
Buku Teks