Sketch by Frithjof Schuon of two Chinese mandarins, 1924. Found in IPMB, p. 198
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.