Bjornson, Gordon B.
Vantage Press , 1971
Buku Teks
Mehta, J.K., author
Caitanya Publishing House, 1967
Buku Teks
Blaug, Mark
Cambridge University Press , 1987
Buku Teks
Enke, Stephen
Prentice-Hal, 1951
Buku Teks
Blaug, Mark
Richard D. Irwin, Inc., 1868
Buku Teks