Voice of America Forum Lectures , 1968
Buku Teks
edited by Robert Clayton Pierce
Thomson Learning, 2001
Buku Teks SO
Office of International Information Programs, 1991
Buku Teks SO
Commager, Henry Steele, selector
Yale University Press, 1950
Buku Teks
Patrick, John
Macmillan, 1984
Buku Teks SO