Simplify the following text for a Grade 15 native English-speaking person.
Original: It was at the end of the 7th century and among the Irish that the compiling of these Annals was first begun -- see the Annals of the Four Masters , the Annals of Ulster , the Annals of Innisfallen and the Annales Cambriae or Annals of Wales , one of the earliest sources for King Arthur .
Simplified: The writing of these Annals was begun at the end of the 7th century and among the Irish -- see the Annals of the Four Masters , the Annals of Ulster , the Annals of Innisfallen and the Annales Cambriae or Annals of Wales , one of the earliest sources for King Arthur .