Combining and comparing : addition and subtration/
Jan Mokros, Susan Jo Russell.
- Menlo Park, Calif. : D. Seymour Publications, c1998.
- 1 v. (various pagings) : ill. ; 28 cm.
- Investigations in number, data and space .
"Developed at TERC, Cambridge, Massachusetts." "Grade 3, also appropriate for Grade 4." Accompanied by: Investigations at home. 21 p.