Churchill Livingstone, 2003
Buku Teks
Weisman, Herman M.
Charles E. Merrill Publishing Company, 1980
Buku Teks
Sklare, Arnold B., author
McGraw-Hill, 1964
Buku Teks
Waldo, Willis H., author
Van Nostrand Reinhold, 1960
Koleksi Publik
Rougier, Harry, author
W.W. Norton, 1970
Buku Teks