Now concerning his sons, and the greatness of the burdens laid upon him, and the repairing of the house of God, behold, they are written in the story of the book of the kings. And Amaziah his son reigned in his stead.

The accounts of the sons of Joash, as well as the many pronouncements about him and about the restoration of the house of God, are indeed written in the Treatise of the Book of the Kings. And his son Amaziah reigned in his place.