Bennett, A., Jr., Maier, E., & Nelson, L. T. (1989). Modeling integers: Unit 6, Math in the mind’s eye. Salem, OR: Math Learning Center.
Eisen, A. P. (1999). Exploring factor sets with a graphing calculator. Mathematics Teaching in the Middle School, 5, 78-82.
Kieran, C., & Chalouh, L. (1993). Prealgebra: The transition from arithmetic to algebra. In D. T. Owens (Ed.), Research ideas for the classroom: Middle grades mathematics (pp. 179-198). Old Tappan, NJ: Macmillan.
Martinez, J. G. R. (1988). Helping students understand factors and terms. Mathematics Teacher, 81, 747-751.
Martinez, J.G. (2002). Building conceptual bridges from arithmetic to algebra. Mathematics Teaching in the Middle School, 7, 326-331.
Slavit, D. (2001). Revisiting a difference of squares. Mathematics Teaching in the Middle School, 6, 378-381.