Abt Associates. (1976). Education as experimentation: A planned variation model (Vol. #3A). Cambridge, MA: Author.
2.
BloomB. S. (1984). The 2 Sigma Problem: The search for methods of group instruction as effective as one-to-one tutoring. Educational Researcher, 13(6), 4–16.
3.
DonnellanA. (1984). The criterion of the least dangerous assumption. Behavioral Disorders, 9(2), 141–150.
4.
EngelmannS. E., & CarnineD. W. (1975). (DISTAR Arithmetic I (2nd ed.). Chicago: Science Research Associates.
5.
HouseE. R., GlassG. V., McLeanL. D., & WalkerD. F., (1978). No simple answer: Critique of the Follow Through evaluation. Harvard Educational Review, 48, 128–160.
6.
LovittT. C. (1971). Rate per minute as an academic measure. Unpublished manuscript, University of Washington, Seattle.
7.
SilbertJ., CarnineD., & SteinM. (1981). Direct Instruction Mathematics. Columbus, OH: Charles Merrill.
8.
SmithD. D., & LovittT. C. (1982). Computational Arithmetic Program. Austin, TX: PRO-ED.
9.
Wiley and Sons. (1967–1974). Nuffield Mathematics Project. New York: Author.