The history of the English people
Here are the two links for the documents I mentioned:
Gildas‘ On the Ruin of Britain: http://www.heroofcamelot.com/docs/Gildas-On-the-Ruin-of-Britain.pdf
The Venerable Bede’s Ecclesiastical History of the English People: http://www.heroofcamelot.com/docs/Bede-Ecclesiastical-History.pdf