Forbes, W. Cameron
Houghton Mifflin, 1928
Buku Teks
Alberts, A.
The University of Massachusetts Press, 1983
Buku Teks
Oliver, Douglas L., author
Harvard University Press, 1951
Buku Teks
Oliver, Douglas L., author
Harvard University Press, 1958.
Buku Teks
Shaw, Bernard, 1856-1950, author
Penguin Books, 1934
Buku Teks