1. The world distribution of gallstones;Brett, M.; Barker, D.J.P.;Int J Epidemiol,1976
2. The epidemiology of gallstones and suggested aetiology;Heaton, K.W.;Clin Gastroenterol,1973
3. Gallstones: geographical and chronological features;Burkitt, D.P.; Tunstall, M.;J Trop Med Hyg,1975
4. Carcinoma of the gallbladder and cholelithiasis on the Witwatersrand: Autopsy survey of the racial incidence;Becker, B.J.P.; Chatgidakis, C.B.;S Afr J Clin Sci,1952
5. Changing state of gallstone disease in;Nakayama, F.; Miyake, H.;Japan. Am J Surg,1970