Ratner, David L.
West Publishing, 1992
Buku Teks SO
Siever, Ellen
O'Reilly, 2003
Buku Teks SO
Folsom, Ralph Haughwout
West Group, 1999
Buku Teks
Arntz, Helmut
The Press and Information Office of the federal Germa Govermant, [1967]
Buku Teks SO
Maraist, Frank L.
West Publishing, 1996
Buku Teks SO