Where do we get the first reference of the Vanga Kingdom?

Q. Where do we get the first reference of the Vanga Kingdom?
Answer: Mahabharata
Notes: In Mahabharata, it was referred that Vanga army was skilled in handling war elephants and they sided with the Kauravas. The boundary of the Vanga kingdom was formed by the Padma and Bhagirathi river in the West, North and East and the South was bounded by the Bay of Bengal.