Raphael Holinshed, Chronicles of England, Scotland and Ireland: England.- v. 5. Scotland.- v. 6 Ireland, 1808, J. Johnson. E-book.
Nick Aitchison, Macbeth Man and Myth, 1999, Stroud, Gloucestershire, Sutton Publishing Limited. Book.
Jonathan Clements, A Brief History of the Vikings, 2005, London, Constable & Robinson Ltd. E-book.
Cameron Taylor, Alistair Murray, On the Trail of the Real Macbeth, King of Alba, 2008, Edinburgh, Luath Press Limited. E-book (2015)
Laurence Larson, Canute the Great, 2016, Ozymandias Press.
Richard Abels, Aethelred the Unready, The Failed King, 2018, Renguin Random House, UK. E-book.
I use Wikipedia mostly to quickly check or verify dates, find links to source texts, and see additional information in various languages, I find a lot of information is inaccurate, outdated, or incomplete. Use Wikipedia with caution, kids!
Video about the Battle of Carham, 1018. https://www.youtube.com/watch?v=YyzSXqxKUnE