1. Aistars, J. (1987). Fatigue in the cancer patient: A conceptual approach to a clinical problem. Oncology Nursing Forum, 14(6), 25–30.
2. Bernard, C. (1957). An introduction to the study of experimental medicine. Chelmsford: Courier Corporation.
3. Bhaskar, R. (2013). A realist theory of science. Abingdon: Routledge.
4. Checkland, P. (1981). Systems thinking, systems practice. New York: Wiley.
5. Grmek, M. D., Cohen, R. S., & Cimino, G. (2012). On scientific discovery: The erice lectures 1977. Berloin: Springer.