Dewett, Kewal Krishan
Premier Publishing Co. , 1969
Buku Teks
Mehta, J.K., author
Caitanya Publishing House, 1967
Buku Teks
Blaug, Mark, author
Cambridge University Press, 1987
Buku Teks
Enke, Stephen, author
Prentice-Hall, 1951
Buku Teks
Bjornson, Gordon B.
Vantage Press , 1971
Buku Teks