University of Chicago, Graduate Library School , 1970
Buku Referensi
Hulgren, Thor
National Bureau of Economic Research; distributed by Columbia University Press, 1965
Buku Teks
Makin, John H.
American Entreprise Institute, 1991
Buku Teks
Brown, Norman
Prentice-Hall, 1998
Buku Teks
Austin, Erik W.
Columbia University Press, 1986
Buku Teks