Our sources upon the councils of Serdica and Philippolis include Socrates Historia Ecclesiastica 2.20. He writes that the ongoing disagreement, including over the restoration of Paul and Athanasius, as well as the creed sent West, leads to Contans requesting and Constantius agreeing to a joint council in Sardica. Socrates dates this to 347. He cites Athanasius as saying that 300 were present, but Athanasius figure includes those who subscribed afterwards or wrote beforehand. Athanasius’ Epistle ad Solitar. c.15 suggests 170 bishops. Upon meeting, the eastern bishops refused to confer with the Westerns unless they first excluded Athanasius and Paul, but Protogenes of Sardica and Hosius of Cordova refused, so the Easterns withdrew to Philippopolis. Socrates reports that the Easterns anathematised homoousios and approved Anomoianism. Meanwhile the westerns confirmed Niceaea, rejected anomoion, recognised homoousion, restored Paul, Athanasius, and Marcellus. Socrates is almost diametrically wrong about anomoion, since the expression does not appear and the statement that the Son is of a different ousia is anathematised.
Theodoret in Historica Ecclesiastica 2.6 gives an introduction to the council, and provides an Encyclical letter from the council including doctrinal material that may or may not be a creed (it lacks a distinct creedal form, but it does follow the standard kind of creedal outline). The letter identifies the Eastern bishops as “Eusebius, Maris, Theodorus, Theognis, Ursacius, Valens, Menophantus, Stephanus.” It relates their unwillingness to meet with the Western-bloc primarily on account of those previously exiled/condemned/deposed, and an unwillingness to justify those actions. Their retreat is taken as proof of the falsehood of their accusations.
The doctrinal material begins by declaring excommunicate those “maintaining that Christ is God but not true God; that he is Son but not True Son” and that “Christ before the ages, they teach a beginning and end to him, not as in time, but have a genesis before all time.”
Here becomes clearer how the Antioch creeds function in terms of what they maintain and what they fail to maintain. The Serdican assembly considers them to be distinguishing between ‘God’ and ‘true God’, and that their statements about the pre-temporal generation of the Son amount to not an eternal pre-existence, but a pre-temporal creation.
They also identify the Easterns as teaching “the hypostaseis of the Father, Son, and Holy Spirit are different”; in contrast to their position that “one hypostasis, which the heretics term ousia”. In contrast, they state that “He could not have always been, if he took a beginning, because the always existing Word has no beginning, and God will abide neverending”. They refer the sonship of the Logos to neither regeneration nor merit, but essence, and distinguish the term Firstborn to refer to his humanity. That the Father is greater than the Son is neither about essence nor difference, but “because the name itself of Gather is greater than of Son”. Specifically concerning John 10:30 they identify their opponent’s interpretation as referring to “concord and harmony”, while they maintain that it is of “because of the unity of hypostasis”.
The Easterns withdrew from Serdica and held a counter-council at Philippopolis. Socrates writes about it in HE 2.20, which we have looked at above under Serdica (he adds little to nothing more than what is mentioned above). Both Socrates and Sozomen think that the creed presented to the Westerns was the Macrostich, but this is also almost certainly wrong, it being a product of Antioch 345, not Antioch 341.
Hilary in De Synodis 34 provides a creedal text from Sardica 343 that is largely equivalent to the 4th Antiochene creed as given above. Hilary gives an overall positive appraisal of the creed, though at this stage Hilary is prepared to state “Since therefore he is anathema who says there are many Gods and he is anathema who denies that the Son is God; it is fully shewn that the fact that each has one and the same name arises from the real character of the similar substance in each” In Hilary’s view the creed avoids solitary monadism on one side and tritheism on the other.
 the consulship of Rufinus and Eusebius
 see, for instance, Karl Joseph von Heferele, Clairk, Oxenha, Plumptre A history of the Christian councils: from the original documents, vol 2. T&T Clark, 1876. p.170.
 Eubesius, Theodorus of Heraclea, Narcissus of Neronias, Stephanus of Antioch, Gorgius of Laodicea, Acacius of Caesarea, Menophantus of Ephesus, Ursacius of Singidunum, Valens of Mursa.
 διαφόρους εἶναι τὰς ὑποστάσεις τοῦ Πατρὸς, καὶ τοῦ Υἱοῦ, καὶ τοῦ ἁγίου Πνεύματος.
 μίαν εἶναι ὑπόστασιν, ἥν αὐτοὶ οἱ αἱρετικοὶ οὐσίαν προσαγορεύουσι
 οὐ πάντοτε γὰρ εἶναι ἠδύνατο, εἰ ἀρχὴν ἔλαβεν, ὅτι ὁ πάντοτε ὢν ἀργχὴν οὐκ ἔχει Λόγος; Θεὸς δὲ οὐδέποτε ὑπομένει τέλος.
 ὅτι αὐτὸ τὸ ὄνομα τοῦ Πατρὸς μεῖζόν ἐστι τοῦ Υἱοῦ
 διὰ τὴν συμφωνίαν καὶ τὴν ὁμόνιαν
 διὰ τὴν τῆς ὑποστάσεως ἑνότητα
 Hilary of Poitiers, "On the Councils, or the Faith of the Easterns", trans. L. Pullan and William Sanday, in , vol. 9a, A Select Library of the Nicene and Post-Nicene Fathers of the Christian Church, Second Series, Volume IX: St. Hilary of Poitiers, John of Damascus ( ed. Philip Schaff and Henry Wace;New York: Christian Literature Company, 1899), 14.