1. First-grade reading groups: Their formation and change;Dreeben,1984
2. The curricular applications of classroom groups;Edwards,1994
3. Inside the primary classroom;Galton,1999
4. Ability grouping in education;Ireson,2001
5. Johnson, D.W., Johnson, F.P., & Stanne, M. (2001). Cooperative learning methods: A meta-analysis. http://www.clcrc.com/pages/cl-methods.html.