The two rules:
(i)Each Gotra was named after a Vedic seer.
(ii) Members of same Gotra could not marry.

Lingayats challenged the idea of caste :
(i)They challenged the idea of pollution attributed to certain groups by Brahmanas.
(ii)They encouraged the practices disapproved in Dharma shastras like post-puberty marriage & re-marriage of widows.

Drainage system of Harappan cities-

(i) The drainage system was planned very carefully.

(ii) Road and streets were laid out along an approximate grid pattern intersecting at right angles.

(iii) Streets were laid out with drains and he drains were covered.

(iv) The houses were built along them. Domestic waste water had to flow into the street drains.

(v) The drains could be cleaned at regular intervals. The drains were made of burnt bricks

Sources to construct the history of Mauryan Empire:

(i) Archaeological finds especially sculptures.

(ii) Accounts of Megasthenes, a Greek ambassador to the court of Chandragupta Maurya.

(iii) Arthashastra composed by Kautilya, traditionally believed to be the minister of Chandragupta.

(iv) Buddhist, Jaina, Puranic literature as well as Sanskrit literary works.

(v) Inscriptions of Asoka on rocks and pillars.

The various stages:

(i) The original story was probably composed by charioteer-bards known as sutas who generally accompanied Kshatriya warriors to the battlefield and composed poems celebrating their victories and other achievements.

(ii) These compositions circulated orally.

(iii) Then, from the fifth century BCE, Brahmanas took over the story and began to commit it to writing.

(iv) The new kings want their itihasa to be recorded and preserved more systematically.

(v) This was the period when the worship of Vishnu was growing in importance, and Krishna, one of the important figures of the epic, was coming to be identified with Vishnu. Subsequently, between c. 200 and 400 CE, large didactic sections resembling the Manusmriti were added. This enormous composition is traditionally attributed to a sage named Vyasa.