Barner, D., Athanasopoulou, A., Chu, J., Lewis, M., Marchand, E., Schneider, R., & Frank, M. (2018). A One-Year Classroom-Randomized Trial of Mental Abacus Instruction for First- and Second-Grade Students. Journal of Numerical Cognition, 3(3), 540-558. https://doi.org/10.5964/jnc.v3i3.106