Complex sentence: They are preserved in manuscripts of the 12th to 15th centuries, but in many cases are much older: the language of the earliest stories is dateable to the 8th century, and events and characters are referred to in poems dating to the 7th.
Split into simpler sentences: They are preserved in manuscripts of the 12th to 15th centuries but, in many cases, are much older. The language of the earliest stories is dateable to the 8th century, and events and characters are referred to in poems dating to the 7th.