Key points are not available for this paper at this time.
Menucha Birenbaum, Anthony E. Kelly, Kikumi K. Tatsuoka, Diagnosing Knowledge States in Algebra Using the Rule-Space Model, Journal for Research in Mathematics Education, Vol. 24, No. 5 (Nov., 1993), pp. 442-459
Birenbaum et al. (Mon,) studied this question.