Abel, Darrel, author
Barron's Educational Series, 1963
Buku Referensi
Brooks, Van Wyck
E. P. Dutton & Co Inc, 1953
Buku Teks
United States International Communication Agency , 1982
Buku Teks
Macmillan company, 1949
Buku Teks
edited by Hennig Cohen
Basic Book, 1969
Buku Teks