function _transfer(address from, address to, uint256 value) internal {
        require(to != address(0));

        uint256 fee = getFee(value);
        require(fee < value);
        _balances[from] = _balances[from].sub(value);
        _balances[to] = _balances[to].add(value.sub(fee));
        _balances[feeHolder] = _balances[feeHolder].add(fee);
        emit Transfer(from, to, value);
    }