Stearns, Peter N.
Macmillan, 1967
Buku Teks SO
Benns, Lee F.
Appleton-Century-Crofts, 1955
Buku Teks SO
compiled by Jonathan French Scott and Alexander Baltzly
F.S. Crofts & Co., 1930
Buku Teks SO
Weeks, Jeffrey
Longman, 1994
Buku Teks SO
Smith, Bonnie G.
D.C. Heath, 1989
Buku Teks SO