Government printing Office, 1969
Buku Teks
Stuart, Graham H. (Graham Henry), 1887-, author
Appleton-Century-Crofts, 1955
Buku Teks
United States Information Agency, 1987
Buku Teks
Neale, A.D., author
Cambridge University Press, 1980
Buku Teks
The America University, [date of publication not identified]
Buku Teks