1. [ Woessmann, L. (2004). How equal are educational opportunities? Family background and student achievement in Europe and the US (CESifo Working Paper Series No. 1162). ]
2. [ Common Core State Standards Initiative. (2010). Common Core State Standards for Mathematics (p. 93): National Governors Association Center for Best Practices (NGA Center) and the Council of Chief State School Officers (CCSSO). ]