Zeitlin, Irving M.
Prentice-Hall, 1981
Buku Teks
Pareto, Vilfredo
Frederick A. Praeger, 1966
Buku Teks
by Pauline Mulholland ... [et al.]
Pitman, 1983
Buku Teks
The Monthly Record,
Majalah, Jurnal, Buletin
Argyle, Barry.
Clarendon Press,, 1972
Buku Teks