"Encountering the Extraordinary". Essay by Dietrich Bonhoeffer (1934), published in "Meditations on the Cross" edited by Manfred Weber and translated by Douglas W. Scott (p. 1), 1998.
Oswald Chambers (2015). “Our Brilliant Heritage / If You Will Be Perfect / Disciples Indeed: The Inheritance of God's Transforming Mind & Heart”, p.135, Discovery House