“…Some researchers have tried to explain the performance differences in terms of teachers' pedagogical content knowledge (Ma, 1999), guidebooks for the teachers (Li, 2004), methods courses provided for preservice teachers (Li, 2002), and how teachers used textbooks (Fan, Chen, Zhu, Qiu, & Hu, 2004;Zhu, 2003). Some have investigated how the teaching of mathematics in classrooms was organized (Chen, Lee, & Stevenson, 1993;Gu, Huang, & Marton, 2004;Hiebert, Gallimore, Garnier, Givvin, Hollingsworth, & Jacobs, 2003;Stevenson & Stigler, 1992;Stigler & Hiebert, 1999;Wang & Murphy, 2004). Some have explored the contributions of textbooks used in terms of types of problems included (Li, 2000;Zhu, 2003), the presentation of specific topics such as ratio and proportion (Lo, Cai, & Watanabe, 2001), arithmetic average (Cai, Lo, & Watanabe, 2002), addition and subtraction of integral expressions (Li, 2000), etc.…”