Complex sentence: The editor suggests that seven cantrefs should amended to three, perhaps Arwystli, Maelienydd, and Elfael; these are mentioned earlier in the list as part of Powys in the time of'Meic Menbis', but no longer such.
Split into simpler sentences: The editor suggests that seven cantrefs should amended to three, perhaps Arwystli, Maelienydd, and Elfael. These are mentioned earlier in the list as part of Powys in the time of'Meic Menbis', but no longer such.