1. Children's mathematical thinking: A developmental framework for pre-school, primary and special education teachers;Baroody,1987
2. Supporting the use of external representations in problem solving: The need for flexible learning environments;Cox;Journal of Artificial Intelligence in Education,1995
3. Basic Number Screening Test;Gilham,1976
4. Research on whole number addition and subtraction;Fuson,1992
5. Children and number;Hughes,1986