* [[Mark H. Ashcraft|Ashcraft, M. H.]] & [[Bennett A. Fierman| Fierman, B. A.]] (1982). Mental Addition in Third, Fourth, and Sixth Graders.- In: Journal of Experimental Child Psychology, Vol. 33, S. 216-234. | * [[Mark H. Ashcraft|Ashcraft, M. H.]] & [[Bennett A. Fierman| Fierman, B. A.]] (1982). Mental Addition in Third, Fourth, and Sixth Graders.- In: Journal of Experimental Child Psychology, Vol. 33, S. 216-234. |