Patranuch Sapchookul. (2005) A comparison of tests for homogeneity of the risk difference when data are sparse. Mahidol University,:ม.ป.ท.Patranuch Sapchookul. 2005. A comparison of tests for homogeneity of the risk difference when data are sparse. ม.ป.ท.:Mahidol University,;Patranuch Sapchookul. A comparison of tests for homogeneity of the risk difference when data are sparse. ม.ป.ท.:Mahidol University, 2005. Print.