सिंधु घाटी सभ्यता के लोग मुख्य रूप से 'गोमेद' (अकीक) किस क्षेत्र से प्राप्त करते थे?

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?