<https://routenote.com/blog/axis-of-awesome-the-only-4-chords-you-need-to-have-a-number-1/#webpage>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<https://routenote.com/blog/axis-of-awesome-the-only-4-chords-you-need-to-have-a-number-1/>