Twining, William, author
Cambridge University Press, 2012
Buku Teks
Llewellyn, Karl N.
Little, Brown and Company, 1960
Buku Teks
Collin, Henry
Macmillan, 1965
Buku Teks
Snyder, Llewellyn R.
McGraw-Hill, 1968
Buku Teks
Luxemburg, Jan van, author
Peter lang, [date of publication not identified]
Buku Teks