Plato, Laws 766c

ταὐτὰ ἄλλον ἐπὶ ταύτην τὴν ἀρχὴν αἱρεῖσθαι.ἐὰν δέ τις δημοσίαν ἀρχὴν ἄρχων ἀποθάνῃ πρὶν ἐξήκειν αὐτῷ τὴν ἀρχὴν πλεῖον ἢ τριάκοντα ἐπιδεομένην ἡμερῶν, τὸν αὐτὸν τρόπον ἐπὶ τὴν ἀρχὴν ἄλλον καθιστάναι οἷς ἦν τοῦτο προσηκόντως μέλον. καὶ ἐὰν ὀρφανῶν ἐπίτροπος τελευτήσῃ τις, οἱ προσήκοντες καὶ ἐπιδημοῦντες πρὸς πατρὸς καὶ μητρὸς μέχρι ἀνεψιῶν παίδων ἄλλον καθιστάντων

in a similar manner. If anyone holding a public office dies more than thirty days before his office terminates, those whose proper duty it is must appoint a substitute in the same manner. If a guardian of orphans dies, the relations, who are residents, on both the father’s and mother’s side, as far as cousin’s children, shall appoint a substitute within ten days, failing which they shall each be fined one drachma per diem