Partridge, Eric, 1894-1979, author
Macmillan, 1959
Buku Referensi
Wise, Hilary
Routledge, 1997
Buku Teks
Pfammatter, Ulrich, author
Birkhauser, 2000
Buku Teks
Reeves, Joan Wynn, author
Penguin books, 1958
Buku Teks
Blomquist, N. Soren
Stockholm Department of Economics University of Stockholm 1982,
Buku Teks