I want to know the answer to the following question:
Who introduced a system of musical notation used in the Balkans in the 14th century?
All the background I'm provided with is that "Prominent reformer of Orthodox Church music from the first half of 14th century was John Kukuzelis; he also introduced a system of notation widely used in the Balkans in the following centuries.". Is that enough to answer the question?
Answer: yes