Tradition
St. Cyprian
The Epistles of Cyprian
Letter 30
The Roman Clergy to Cyprian.
Argument.— The Roman Clergy Enter into the Matters Which They Had Spoken of in the Foregoing Letter, More Fully and Substantially in the Present One; Replying, Moreover, to Another Letter of Cyprian, Which is Thought Not to Be Extant, and from Which They Quote a Few Words. They Thank Cyprian for His Letters Sent to the Roman Confessors and Martyrs.
Source: The Epistles of Cyprian (New Advent)