Maier, Norman R.F.
John Wiley & Sons, 1960
Buku Teks
Nierenberg, Alan H., author
American Management Association, 2005
eBooks
Poundstone, William, author
Little, Brown, 2012
Buku Teks
Spradley, James P.
Halt, Rinehart and Winston, 1979
Buku Teks
Cambridge University Press, 1997
eBooks