Pettit, Philip H.
English Language Book Society , 1985
Buku Teks
Hudson, Alastair, author
Cavendish Publishing Limited, 2003
Buku Teks
Todd, Paul, author
London : Balckstone, 1994,
Buku Referensi
Haley, Michael, author
Sweet and Maxwell, 2007
Buku Teks
Penner, J. E. (James E.), author
Oxford University Press, 2016
Buku Teks