Kitchenham, B. A., Brereton, P., Turner, M., Niazi, M. K., Linkman, S., Pretorius, R., & Budgen, D. (2010). Refining the systematic literature review process--two participant-observer case studies. Empirical Software Engineering, 15(6), 618-653. https://doi.org/10.1007/s10664-010-9134-8