Rommen, Heinrich A.
Liberty Fund Indianapolis, 1998
Buku Teks
Wilson, Charles, author
Cassell, 1970
Buku Teks
Anderson, Robert T.
Wadsworth, 1971
Buku Teks
Hudson, G. F., author
Clarendon Press , 1937
Buku Teks
Lovejoy, Arthur O.
Harper Torchbooks, 1960
Buku Teks