Williams, T. Harry, author
Alfred A. Knopf, 1963
Buku Teks
Myers, Gustavus, author
Random House, 1943
Buku Teks
Myers, Margaret G., author
Columbia University Press , 1970
Buku Teks
Kemmerer, Donald L., author
Littlefield, Adams, 1956
Buku Teks
Rae, John B., author
Mc Graw-Hill Book Company, 1949
Buku Teks