Gardner, Richard N.
Dell Publishing Co., Inc., 1965
Buku Teks
Corwin, Edward S., author
Princeton University Press, 1944
Buku Teks
Kirgis, Frederic L., author
West Publishing, 1993
Buku Teks
edited by Evan Luard
Praeger, 1966
Buku Teks
Peaslee, Amos J., author
Martinus Nijhoff, 1956
Buku Teks