Hickman, Bert G., author
The Brooking Institution , 1965
Buku Teks
Hughes, E. R.
Hutchinson's University Library, 1950
Buku Teks
Hughes, H. Stuart
Frentice Hall,, 1961
Buku Teks
Hughes, Edward, author
Longman, 1995
Buku Teks
Hughes, Edward, author
John Wiley & Sons, 1987
Buku Teks