A sketch of a Muslim man by Frithjof Schuon, including some calligraphy of the first sura in the Koran. Found in IPMB, p. 185
Christentum – Islam: Ausblicke auf eine esoterisch Ökumene (e-Book)
In this work, Frithjof Schuon compares Christianity and Islam and also looks at confessions within these world religions: Protestantism, Orthodoxy, and Shiism.