    function mint(address _to, uint256 _amount, address _owner) internal returns (bool) {
        require(_to != address(0));
        require(_amount <= balances[_owner]);
        balances[_to] = balances[_to].add(_amount);
        balances[_owner] = balances[_owner].sub(_amount);
        emit Transfer(_owner, _to, _amount);
        return true;
    }