M. Kimani, J. Kiiru, M. Matu, T. Chokwe, and H. Saidi, “Evaluation of POSSUM and P-POSSUM as predictors of mortality and morbidity in patients undergoing laparotomy at a referral hospital in Nairobi, Kenya”, Ann Afr Surg., vol. 5, no. 1, Apr. 2010.