Nor is it known for sure which liturgy, that of Rome or that of Constantinople, they took as a source. They may well have used the Roman alphabet, as suggested by liturgical fragments which adhere closely to the Latin type. This view is confirmed by the "Prague Fragments" and by certain Old Glagolitic liturgical fragments brought from Jerusalem to Kiev and discovered there by Izmail Sreznevsky—probably the oldest document for the Slavonic tongue; these adhere closely to the Latin type, as is shown by the words ""Mass,"" ""Preface,"" and the name of one Felicitas. In any case, the circumstances were such that the brothers could hope for no permanent success without obtaining the authorization of Rome.