Wilber, K., & Wilber, T. K. (2000). Grace and grit: Spirituality and healing in the life and death of Treya Killam Wilber (Second edition.). Shambhala.
Chicago-viite (17. p.)Wilber, Ken, ja Treya Killam Wilber. Grace and Grit: Spirituality and Healing in the Life and Death of Treya Killam Wilber. Second edition. Boston: Shambhala, 2000.
MLA-viite (9. p.)Wilber, Ken, ja Treya Killam Wilber. Grace and Grit: Spirituality and Healing in the Life and Death of Treya Killam Wilber. Second edition. Shambhala, 2000.
Varoitus: Nämä viitteet eivät aina ole täysin luotettavia.