1. Consider two populations denoted by A and B
2. Natural history of stroke in Rochester, Minnesota, 1945 with age-specific incidence rates given through 1954;Whisnant, J.P.; Fitzgibbons, J.P.; Kurland, L.T.; Sayre, G.P.;Stroke,1971
3. Natural history of stroke in Rochester, Minnesota, 1955 through 1969: an extension of a previous study 1945 through 1954;Matsumoto, N.; Whisnant, J.P.; Kurland, L.T.; Okazaki, H.;Stroke,1973
4. qB=XNNXqB in a defined population, Middlesex County, Connecticut. JA,1968
5. n Intern Med 1971; 128: 949-55.