Sources:
http://www.ascd.org/publications/educational-leadership/oct10/vol68/num02/Lessons-of-Mastery-Learning.aspx
https://www.springpointschools.org/blog/2016/01/five-key-lessons-mastery-startup/
http://www.redesignu.org/sites/default/files/uploads/Making-Mastery-Work-NMEF-2012-Inline.pdf
https://sites.google.com/a/philasd.org/competencyeducation/
