Field, Oliver P
Harper, 1949
Buku Teks
Dodd, Walter Fairleigh, 1880-1960, author
Century, 1923
Buku Teks
Cox, George H., author
Wadsworth/Thomson Learning, Belmont, CA, 2001
Buku Teks SO
Holloway, William Vernon, author
McGraw-Hill , 1951
Buku Teks
Fordham, Jefferson B.
University of Pennsylvania Press, 1959
Buku Teks