²³ Edward Williams, ‘A Byzantine Ars Nova: The 14th-Century Reforms Of John Koukouzeles in the Chanting of Great Vespers’, ed. by H. Birnbaum and S. Vryonis, Aspects of the Balkans. Continuity and change. Contributions to the International Balkan Conference held at UCLA, October 23-28, 1969, (Los Angeles, CA: MOUTON, 1972), 212-229.