Luther Digest: An Annual Abridgment of Luther Studies, Volumes 2-4, s. 146. Luther Academy, 1994. Teoksen verkkoversio. (englanti)
christiancentury.org
Daniels: Martin Luther's fascination with Ethiopian Christianity 31 October 2017. The Christian Century. ”Luther extended full fellowship to Deacon Michael and the Ethiopian Church, an invitation Luther withheld from the Bohemian Brethren (the Hussites) and Reformed Churches connected to Ulrich Zwingli.” Viitattu 9 April 2018. (englanti)
