According to Michael Barber, in the Septuagint, the Torah and Nevi'im are established as canonical, but the "Ketuvim" appear not to have been definitively canonized yet. The translation (and editing) work might have been done by seventy (or seventy-two) elders who translated the Hebrew Bible into Koine Greek but the historical evidence for this story is rather sketchy. Beyond that, according to him, it is virtually impossible to determine when each of the other various books was incorporated into the Septuagint.