Passage 6.12.9
οὐδέ τινα ἔστιν ἐν Ἕλλησι Τρίτειαν πόλιν ἄλλην γε ἢ τὴν Ἀχαιῶν εὑρεῖν. τηνικαῦτα γοῦν ἐς Ἀρκάδας ἡγοῖτο ἄν τις συντελέσαι τοὺς Τριταιεῖς, καθὰ καὶ νῦν ἔτι Ἀρκάδων αὐτῶν εἰσιν οἱ ἐς τὸ Ἀργολικὸν τελοῦντες. τοῦ Ἀγησάρχου δέ ἐστιν ἡ εἰκὼν τέχνη τῶν Πολυκλέους παίδων . τούτων μὲν δὴ ποιησόμεθα μνήμην καὶ ἐν τοῖς ὑστέροις τοῦ λόγου·
Nor indeed is it possible to find another Greek city named Triteia aside from this one of the Achaeans. At that time one would certainly have reckoned the Triteians among the Arcadians, just as even now those of the Arcadians living within Argolis still pay tribute. The image of Agesarchus is the work of the sons of Polycleitus. Of these we shall make mention also later in our narrative.