United State Information Agency, 1994
Buku Teks SO
Abel, Darrel
Barron's Educational Series, 1963
Buku Referensi
Wachner, Clarence W.
Macmillan, 1963
Buku Teks SO
edited by Hennig Cohen
Basic Book, 1969
Buku Teks SO
edited by Richard Kostelanetz
United States International Communication Agency, 1982
Buku Teks SO