Parks, Wallace Judson, author
Johns Hopkins Press, 1951
Buku Teks
Aubrey, Henry G., author
Frederick A. Praeger, 1964
Buku Teks
Fisher, Bart S.
Little, Brown and Company, 1989
Buku Teks
Jackson, John H., author
St.Paul,Minn., 1995
Buku Teks
Martinus Nijhoff , 1990
Buku Teks