Einzig, Paul
Eyre & Spottiswood , 1949
Buku Teks
Tripp, Charles
Cambridge University Press, 2006
Buku Teks
Nash, Manning
Chandler Publishing Company, 1966
Buku Teks
Hoselitz, Bert F.
Free Press of Glencoe, 1960
Buku Teks
Weil, David N.
Pearsons Addison-Wesley, 2009
Buku Teks