Stromberg, Roland N.
Prentice-Hall, 1990
Buku Teks
Stromberg, Roland N.
Prentice-Hall, 1997
Buku Teks
Benns, Lee F.
Appleton-Century-Crofts, 1955
Buku Teks
compiled by Jonathan French Scott and Alexander Baltzly
F.S. Crofts & Co., 1930
Buku Teks
Stearns, Peter N.
Macmillan, 1967
Buku Teks