Church History by Eusebius Pamphilius
On Bk. VII. chap. 26, § 1 (note 4, continued).
On Dionysius' attitude toward Sabellianism and the occasion of the Apology (?lenchos kai apologia) in four books, which he addressed to Dionysius of Rome, see Bk. VI. chap.40, note 1. This work is no longer extant, but brief fragments of it have been preserved by Athanasius (in his De Sent. Dionysii) and by Basil ( in his De Spir. Sancto). English translation in the Ante-Nicene Fathers, Vol. VI. p.92 sq. The longer work was preceded by a shorter one, now lost, to which reference is made in one of the fragments of the longer work. We do not know the exact date of the work, but may assign it with considerable probability to the earlier part of the episcopate of Dionysius of Rome; that is, soon after 259. Upon this work and upon Dionysius' attitude toward Sabellianism, see especially Dittrich, Dionysius der Grosse, p.91. sq.