Complex sentence: Eric's Chronicle ("Erikskrönikan" in Swedish) is the oldest surviving Swedish chronicle written by an unknown author (or, less probably, several authors) between about 1320 and 1335.
Split into simpler sentences: Eric's Chronicle (Swedish: "Erikskrönikan") is the oldest surviving Swedish chronicle. It was written by an unknown author (or, less probably, several authors) between about 1320 and 1335.