editor, George Clack
[Publisher not identified], 1997
Buku Teks SO
Davis, Gwenn
London : Mansell Publishing Limited, 1991,
Buku Referensi
edited by Richard Kostelanetz
United States International Communication Agency, 1982
Buku Teks SO
edited by Richard Kostelanetz
United States International Communication Agency, 1982
Buku Teks SO
edited by Don M. Wolfe
Hendrick House, 1955
Buku Teks SO