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