Complex sentence: This particular type of a fully notated tonary only appears in Burgundy and Normandy, so it can be regarded as a characteristic document of a certain school founded by William of Volpiano, who was reforming abbot at St. Benignus of Dijon since 989.
Split into simpler sentences: This particular type of a fully notated tonary only appears in Burgundy and Normandy. It can be regarded as a characteristic document of a certain school founded by William of Volpiano, who was reforming abbot at St. Benignus of Dijon since 989.