Cochran, Thomas C.
McGraw-Hill, 1972
Buku Teks SO
Bailey, Thomas Andrew, 1902-1983
D.C. Healt, 1987
Buku Teks
Herget, James E.
Texas: Rice University Press, 1990,
Buku Referensi
Ferrell, Robert H.
W.W. Norton, 1959
Buku Teks
Morris, Richard B.
Harper & Row, 1961
Buku Teks SO