1. Stefanek M, McDonald PG, Hess SA. Religion, spirituality and cancer: current status and methodological challenges. Psychooncology. 2005;14:450–63.
2. Fetzer Institute. Multidimensional measurement of religiousness, spirituality for use in health research. A report of a National Working Group supported by the Fetzer Institute in collaboration with the National Institute on Ageing. Kalamazoo, MI: Fetzer Institute; 2003.
3. Spilka, B. Spirituality: problems and directions in operationalizing a fuzzy concept. Paper presented at the meeting of the American Psychological Association, Toronto, Ontario, 1993.
4. Sheldrake P. Spirituality and history: questions of interpretations and method. New York: Crossroads; 1992.
5. Wulff DM. Psychology of religion: classic and contemporary. 2nd ed. New York: Wiley; 1997.