The Library of Ashurbanipal (668-630/627 BCE) was composed of several collections that formed the reference collection of the kings of Assyria in Nineveh in the 7th century BCE. It is difficult to say exactly how many tablets have been discovered in this library. They number roughly 15,000 to date. Inventories of wax-covered wooden tablets, better known as wax tablets, suggest clay was not the only material used to write literary and learned texts. None have survived. The library at Nineveh is attributed to Ashurbanipal, although his father Esarhaddon had already worked a lot on it.Ashurbanipal considerably added to its collections, as shown by the letters he sent into Babylonia requesting tablets. The library was abandoned after the destruction of Nineveh in 612. However, some tablets did find their way to Uruk.