प्राचीन भारत में, उस विधवा के लिए किस शब्द का प्रयोग किया जाता था जिसका पुनर्विवाह हो जाता था?

In Ancient Indian Statecraft, Kautilya's 'Rajamandala' theory primarily deals with:

The First Buddhist Council was held at ______.

Which ancient Indian text contains references indicating that population counts or census-like records were maintained in ancient India?