function doBurn(address _operator, address _tokenHolder, uint256 _amount, bytes _holderData, bytes _operatorData)
        internal
    {
        requireMultiple(_amount);
        require(balanceOf(_tokenHolder) >= _amount);

        mBalances[_tokenHolder] = mBalances[_tokenHolder].sub(_amount);
        mTotalSupply = mTotalSupply.sub(_amount);

        callSender(_operator, _tokenHolder, 0x0, _amount, _holderData, _operatorData);
        emit Burned(_operator, _tokenHolder, _amount, _holderData, _operatorData);
    }