Llewellyn, Karl N.
Little,Brown and Company, 1960
Buku Teks
Twining, William
Cambridge University Press, 2012
Buku Teks
Holmes, Oliver Wendell, Jr.
Little, Brown and Company, 1951
Buku Teks
Okoye, Adaeze
NY Routledge, 2017
Buku Teks
Eisenberg, Melvin A.
Harvard University Press, 1988
Buku Teks