Edgar, Donald Ernest
Prentice-Hall, 1980
Buku Teks
Zeitlin, Irving M., author
Prentice-Hall, 1981
Buku Teks
Pareto, Vilfredo, author
Frederick A. Praeger, 1966
Buku Teks
by Pauline Mulholland ... [et al.]
Pitman, 1983
Buku Teks
The Monthly Record,
Majalah, Jurnal, Buletin