σφῶι
From LSJ
εἰ πλείονα δ' εἰδείης Σισύφου → if you were more intelligent than Sisyphus
Greek (Liddell-Scott)
σφῶι: δυϊκ. ἀρσ. καὶ θηλ. τῆς ἀντωνυμίας τοῦ β΄ προσώπου, = ὑμεῖς οἱ δύο ἴδε σὺ ΙΙ.
English (Autenrieth)
gen. and dat. σφῶιν, σφῷν: dual of σύ, ye two, you two, you both, Il. 1.336, , Il. 11.776, . σφῶι and σφῶιν are never enclitic.
Dutch (Woordenboekgrieks.nl)
σφῶι, pron. pers., 2 dual. nom. en acc.., m. en f.. zie σύ.