Chogyam Trungpa (2010). “The Collected Works of Chogyam Trungpa: Volume Eight: Great Eastern Sun; Shambhala; Selected Writings”, p.38, Shambhala Publications
Martin Dugard (2011). “To Be a Runner: How Racing Up Mountains, Running with the Bulls, or Just Taking On a 5-K Makes You a Better Person (and the World a Better Place)”, p.15, Rodale