Which primary sources would allow a historian to show that akkadian was a popular language?

Explanation:

It is known that Akkad (also given as Agade) was a city located along the western bank of the Euphrates River possibly between the cities of Sippar and Kish (or, perhaps, between Mari and Babylon or, even, elsewhere along the Euphrates).The language of the city, Akkadian, was already in use before the rise of the Akkadian Empire (notably in the wealthy city of Mari where vast cuneiform tablets have helped to define events for later historians) and it is possible that Sargon restored Akkad, rather than built it. It should also be noted that Sargon was not the first ruler to unite the disparate cities and tribes under one rule. The King of Uruk, Lugalzagesi, had already accomplished this, though on a much smaller scale, under his own rule