Two years later, the Emperor Valens, who favored the Arian position, in his turn exiled Athanasius. This time however, Athanasius simply left for the outskirts of Alexandria, where he stayed for only a few months before the local authorities convinced Valens to retract his order of exile. Some early reports state that Athanasius spent this period of exile at his family's ancestral tomb in a Christian cemetery. It was during this period, the final exile, that he is said to have spent four months in hiding in his father's tomb. (Soz., "Hist. Eccl.", VI, xii; Soc., "Hist. Eccl.", IV, xii).
Try to answer this question if possible (otherwise reply "unanswerable"):  Who didn't convince Valens to let him return to Alexandria?
unanswerable