RT Article T1 Crises and anxieties in Fifteenth Century Byzantium: The Reassertion of Old, And the Emergence or New Cultural Forms JF Islamic and middle eastern societies SP 100 OP 126 A1 Vryonis, Speros 1928-2019 LA English YR 1987 UL https://ixtheo.de/Record/1962457621 SN 0915597462