edited by Robert Clayton Pierce
Thomson Learning, 2001
Buku Teks SO
Commager, Henry Steele, selector
Yale University Press, 1950
Buku Teks
Voice of America Forum Lectures , 1968
Buku Teks
Barnes, Harry Elmer
Prentice-Hall, 1950
Buku Teks SO
Simpson, David
Oxford University Press , 1986
Buku Teks SO