"Content and Form: Authorship Attribution and Pseudonymity in Ancient Speeches, Letters, Lectures, and Translations —A Rejoinder to Bart Ehrman," JBL 136.2 (2017): 381–403.
In this article Baum cites several ancient Christian and non-Christian Greco-Roman primary sources to support his thesis that,
"Everywhere an authorial attribution was regarded as correct and nondeceptive if either the wording or the content of a particular text could be traced back to the author whose name it carried." (pg. 402)In one interesting section, Baum discusses the Christian tradition that, even though Mark and Luke "composed" gospels that bore their names, Peter (for Mark) and Paul (for Luke), "were regarded as the intellectual authors of their contents (pg. 390)." Baum shows this attitude by siting the statements of Tertullian,
"That which Mark edited is stated to be Peter’s [Petri affirmetur], whose interpreter Mark was. Luke’s digest also they usually attribute to Paul [Paulo adscribere solent]. It is permissible for the works which disciples published to be regarded as belonging to their masters [Capit magistrorum videri quae discipuli promulgarint]." (Marc. 4.5.3–4)(Baum, pg. 390)Another source not referenced by Baum support's this conclusion, Papias's (ca. 100-110 CE) statements on the composition of Mark.
"And the Elder used to say this: 'Mark, having become Peter's interpreter, wrote down accurately everything he remembered, though not in order, of the things either said or done by Christ. For he neither heard the Lord nor followed him, but afterward, as I said, followed Peter, who adapted his teachings as needed but had no intention of giving an ordered account of the Lord's sayings. Consequently Mark did nothing wrong in writing down some things as he remembered them, for he made it his one concern not omit anything which he heard or to make any false statement in them." (Eusebius, Hist. eccl. 3.39; Holmes, 569)It is clear that, though Papias acknowledged that his gospel was composed and written down by Mark, he considered Peter as the true "intellectual author."
Galen (ca. 160s-170s CE), In the midst of analyzing the textual work and editions of two former Hippocratic scholars who were active in the first part of the second century, Galen wrote;
"A second book written in place of one formerly written is said to be revised (επιδιεσκευασθαι), when it has the same 'hypothesis'(υποθεσις) and most of the same words; some (of the words) taken out from the former work; some added; some altered. If you want an example of this for the sake of clarity, you have the second Autolycus of Eupolis revised from the former. Thus the doctors from Cnidus published the second 'Cnidian Opinions'in place of the former ones; some having the same in every way; but some added; some taken away; just as some altered. This then is the second book of Hippocrates which they say is more medical than the former." (Hipp. vict. acut. 120.5-14; Scherbenske's translation)Though Galen is speaking specifically in reference to editing an ancient author's work, it is clear that Galen saw that a work was still considered to be that of the ancient authors as long as "some of the words" were still from the original author and that the editing did not alter the original ideas.
Thus, both Papias and Galen confirm Baum's conclusion that,
"Everywhere an authorial attribution was regarded as correct and nondeceptive if either the wording or the content of a particular text could be traced back to the author whose name it carried." (pg. 402)
Holmes, Michael W., ed. The Apostolic Fathers: Greek texts and English translations. Grand Rapids: Baker Books, 1999.
Scherbenske, Eric W. Canonizing Paul: Ancient Editorial Practice and the Corpus Paulinum (Oxford: Oxford University Press, 2013), 39