https://docdrop.org/pdf/The-AB-Guide-Part-I-7w41e.pdf/
https://docdrop.org/pdf/Music-Theory-in-Practice-Grade-6-Peter-Aston-Julian-Webb--v3l4d_ocr.pdf/?src=ocr
https://docdrop.org/pdf/The-AB-Guide-to-Music-Theory-Part-II-ik7b8.pdf/
https://docdrop.org/pdf/010---AB-outline-6-8-2020-3x7bn.pdf/