Louise Hay, What Is Mirror Work? https://www.louisehay.com/what-is-mirror-work/.
Charlotte van Oyen Witvliet, Thomas E. Ludwig, and Kelly L. Vander Laan, Granting Forgiveness or Harboring Grudges: Implications for Emotion, Physiology and Health, https://journals.sagepub.com/doi/10.1111/1467-9280.00320.