Cohen, L., Manion, L., Morrison, K., Bell, R., Martin, S., McCulloch, G., & O'Sullivan, C. (2011). Research methods in education (7. edition.). London: Routledge Taylor & Francis Group.

Cohen, Louis, Lawrence Manion, Keith Morrison, Richard Bell, Stewart Martin, Gary McCulloch, and Carmel O'Sullivan. Research Methods in Education. 7. edition. London: Routledge Taylor & Francis Group, 2011.

Cohen, Louis, et al. Research Methods in Education. 7. edition. London: Routledge Taylor & Francis Group, 2011.