Giles, Judy, author
Blacwell Publisher, 2008
Buku Teks
Routledge, 1997
Buku Teks
Barry Dufour ,Will Curtis
McGraw-Hill, 2011
Buku Teks
Plummer, David T., author
MacGraw-Hill, 1978
Buku Teks
Shetter, William Z., author
Martinus Nijhoff, 1988
Buku Teks