The third zone is politically peripheral to the Empire and includeds its territories, from Sanghol to Mathura, in the vicinity of the Ganges river and its tributaries.
It is fair to call this region Indian because it shares a script, Brahmi, and an artistic style with the regions to the east and south that form the modern state of India.
And thought there is some relevant literature a lot of the types of literature that might be interesting, such as diaries or personal letters, do not survive (if given fairly low levels of literacy they ever existed at all).
So it is the artistic images which must be the principal object of study.
In the north of the Empire, Bactria, those parts of modern Afghanistan, the inscriptions are usually found in Greek script and in the Bactrian language and the art shows strong influences from Parthia and the Steppe.
'Beauty is in the Eye of the Beholder' is an old cliche: That beauty is a subjective matter which depends on individual prejudices.
If beauty were truly subjective, if it depended entirely on our perception it could not be studied.
This sort of study has revealed a huge amount about the relationship between public images and individual perceptions of beauty in modern Europe.
In ancient India only the public image survives - statues, paintings, and carvings.