00465naa#a2200169#i#450# EN\INFRA-M\bibl\6185 20241223184829.1 1998-0728 20150617b2015####ek#y0engy0150####ca RUS RU Problem Situations at Primary School Lesson Journal article Moscow INFRA-M Academic Publishing LLC. 2015 3 с. Journal article local Varanitsa L. naukaru.ru