Guerard, ALbert
Ann Arbor The University of Michigan 1959
Buku Teks
Cobban, Alfred, author
[publisher not identified], [date of publication no identified]
Buku Teks
Cobban, Alfred, author
Braziller, 1965
Buku Teks
Cobban, Alfred, author
Penguin Books, 1990
Buku Teks
Roe, F.C.
Longmans, Green , 1956
Buku Teks