function 	withdrawToken( address token, uint amount ) public {
		assertToken( token );
		assertQuantity( amount );
		if ( Token( token ).transfer( msg.sender, amount ) == false ) {
			revert();
		}
		tokens[token][msg.sender] = safeSub( tokens[token][msg.sender], amount ); 
	    emit Withdraw( token, msg.sender, amount, tokens[token][msg.sender] );
	}