Zbrodoff, NJ (1995). Why is 9+7 harder than 2+3  Strength and Interference as Explanations of the ProblemSize Effect. Memory & Cognition 23(6), 689700.
This work cites the following items of the Benford Online Bibliography:
Ashcraft, MH (1992). Cognitive arithmetic: A review of data and theory. Cognition 44 (Aug), pp. 75106. ISSN/ISBN:00100277. DOI:10.1016/00100277(92)90051I.





Ashcraft, MH and Christy, KS (1995). The Frequency of Arithmetic Facts in Elementary Texts: Addition and Multiplication in Grades 16. Journal for Research in Mathematics Education 26(5), pp. 396421.





Benford, F (1938). The law of anomalous numbers. Proceedings of the American Philosophical Society, Vol. 78, No. 4 (Mar. 31, 1938), pp. 551572.




