00675naa#a2200181#i#450# EN\INFRA-M\bibl\27860 20240724132502.3 2500-3305 20190312b2019####ek#y0engy0150####ca RUS RU The state of basic learning activities in pupils with mental retardation on the example of solving arithmetic problems Journal article Moscow INFRA-M Academic Publishing LLC. 2019 6 с. Journal article local Образование. Воспитание. Обучение. Организация досуга. 37 RUS Skira Elena Vasil'evna naukaru.ru