Do Jews accept The Book of the Wars of the Lord (סֵפֶר מִלְחֲמֹת יהוה) as an authentic part of Tanach?
"From there they set out and camped on the other side of the Arnon, which is in the desert and bounding the Amorite territory. For Arnon is the border of Moab, between Moab and the Amorites. That is why the Book of the Wars of the LORD says: '... Waheb in Suphah and the ravines of Arnon, and at the stream of the ravines that lead to the dwelling of Ar, which lies along the border of Moab.'" Numbers 21:14-15