Woolley, Tyler A.
Burgess, 1969
Buku Teks SO
Ruppert, Edward E.
Saunders College, 1994
Buku Teks SO
edited by D.T. Anderson
Melbourne, 1998
Buku Teks SO
Buchsbaum, Ralph
Chicago The University of Chicago Press, [date of publication not identified],
Buku Teks
Wilmoth, James H.
Prentice-Hall, 1967
Buku Teks SO