Raghunathan K, Layton JB, Ohnuma T, Shaw AD. Observational research using propensity scores. Adv Chronic Kidney Dis. 2016 Nov;23(6):367-72. doi: 10.1053/j.ackd.2016.11.010
Webster AJ, Saville C, Church BM, Gnanasakthy A, Moss R. Some effects of different rearing systems on health, cleanliness and injury in calves. Vet J. 1985 Sep;141(5):472-83.
Webster AJ, Saville C, Church BM, Gnanasakthy A, Moss R. The effect of different rearing systems on the development of calf behaviour. Vet J. 1985 May;141(3):249-64.