Desmond Tutu, John Webster (1982). “Bishop Desmond Tutu, the voice of one crying in the wilderness: a collection of his recent statements in the struggle for justice in South Africa”
Naomi E. Maurer, Vincent van Gogh, Paul Gauguin (1998). “The Pursuit of Spiritual Wisdom: The Thought and Art of Vincent Van Gogh and Paul Gauguin”, p.35, Fairleigh Dickinson Univ Press