Mott, Graham
Pitman, 1997
Buku Teks
Arntz, Helmut
The Press and Information Office of the federal Germa Govermant, [1967]
Buku Teks SO
Harrison, Ian W.
McGraw-Hill, 1973
Buku Teks SO
edited by Philip M. Hauser and Otis Dudley Duncan
The University of Chicago Press, 1959
Buku Teks
Hawkins, Christopher James
Macmillan, 1971
Buku Teks SO