These overviews provide a brief summary of the major content as well as references to the major, supporting, and additional work clusters and mathematical practices in each unit. The K–8 Publisher’s Criteria for the Common Core State Standards for Mathematics has identified the standards in every grade as being the major work, supporting work, or additional work of the grade. It calls for at least 65% of time to be devoted to the major work of the grade with supporting work and additional work engaging students in the major work of the grade where appropriate. The designations are by CCSSM clusters. For example, 3.OA.A Represent and solve problems involving multiplication and division, is the cluster covering standards 3.OA.A.1–3.OA.A.4. See http://achievethecore.org/shifts-mathematics for complete grade level focus breakdowns.