    function transferFrom(address _from, address _to, uint256 _value) public returns (bool success) {
        require (_to != address(0));
		require (_value > 0); 
        require (balanceOf[_from] >= _value) ;
        require (balanceOf[_to] + _value > balanceOf[_to]);
        require (_value <= allowance[_from][msg.sender]);
        balanceOf[_from] = SafeMath.safeSub(balanceOf[_from], _value);
        balanceOf[_to] = SafeMath.safeAdd(balanceOf[_to], _value);
        allowance[_from][msg.sender] = SafeMath.safeSub(allowance[_from][msg.sender], _value);
        emit Transfer(_from, _to, _value);
        return true;
    }