Kaplan, Robert M.
Allyn and Bacon, 1987
Buku Teks SO
Hammond, Kenneth R.
Alfred A. Knopf, 1963
Buku Teks SO
Hammond, Kenneth R.
Alfred A. Knopf , 1962
Buku Teks SO
Siegel, Sidney, 1916-1961
Armico, 1985
Buku Teks SO
Erickson, Bonnie H.
Open University Press, 1977
Buku Teks SO