The subject of a contract in law is defined as the element which the party that owes money commits to do. The subject could be performance of an action, refraining from the performance of an action or a transfer of the right to some property.
Source: Kharofa, Ala’ Eddin. Transactions in Islamic Law. 2nd ed. Kuala Lumpur: A.S. Noordeen, 2000. 22.
Concepts in Islamic Economics and Finance 
Here are some links that I believe will be interested
Bush goes ballistic about other countries being evil and dangerous, because they have weapons of mass destruction. But, he insists on building up even a more deadly supply of nuclear arms right here in the US. What do you think? Why has bush turned our country from a country of hope and prosperity to a country of belligerence and fear.
Are we safer today than we were before?
We have lost friends and influenced no one. No wonder most of the world thinks we suck. Thanks to what george bush has done to our country during the past three years, we do!
This article is really helpful for getting a general knowledge about Islamic Economics. However, you can read this one for more information about;
http://islam-economy.org/why-interest-is-prohibited-in-islam/