I am again grateful to John Briscoe for his many suggestions and corrections on earlier drafts, especially in the textual notes.
As he has noted in his discussion of the Spirensian tradition, in Books 26–30 (Vol. V, pp. lxxx–lxxxii), Σ indicates the reading of the Spirensian tradition if it is either cited by Rhenanus or found in at least two of the other witnesses, while Σ? indicates a reading found in only one such witness. On some occasions, however, it has seemed to him desirable to cite in a parenthesis individual witnesses other than those that have the reading attributed to Σ.