McIntosh, Jane
Checkmark Books, 1999
Buku Referensi
Cochrane, Susan H.
Johns Hopkins University Press, 1979
Buku Teks SO
Rabe, Cynthia Barton
American Management Association, 2006
eBooks
Overstreet, Harry
W.W. Norton, 1958
Buku Teks SO
Dawkins, Richard, 1941-
Black Swan, 2012
Buku Teks SO