Two way sync NC and Google calendars - is it possible?

I know this has been asked before but gave not found a convincing answer.
I can import a calendar from Google, but it does not sync back. I guess I can do the reverse also.
I would like to have 2way sync. It seems that some programs, like Thunderbird, can sync with both NC and Google? Can it be used as an intermediate to sync both ways? Any other solution?