M. Khaer, A. Y. Mansyur, A. Ridfah, and A. A. Ridha, “The Effectiveness Of Writing The Letter Of Gratitude Technique In Reducing The Stress Level Of Islamic Boarding School Student”, Psikis, vol. 7, no. 1, pp. 79–85, Jun. 2021, doi: 10.19109/psikis.v7i1.4612.