Passage 9.34.9
πρότερον δὲ ἔτι τούτων Ἀνδρεὺς Εὐίππην θυγατέρα Λεύκωνος λαμβάνει παρὰ Ἀθάμαντος γυναῖκα, καὶ υἱὸς Ἐτεοκλῆς αὐτῷ γίνεται, Κηφισοῦ δὲ τοῦ ποταμοῦ κατὰ τῶν πολιτῶν τὴν φήμην, ὥστε καὶ τῶν ποιησάντων τινὲς Κηφισιάδην τὸν Ἐτεοκλέα ἐκάλεσαν ἐν τοῖς ἔπεσιν.
Yet even before these events, Andreus took Euippe, daughter of Leucon, as a wife from Athamas, and she bore him a son named Eteocles. According to local tradition, however, Eteocles' father was said to be the river Cephisus, so that some among the poets even called him Cephisiades ("son of Cephisus") in their verses.