00522naa#a2200169#i#450# EN\INFRA-M\bibl\15333 20240506211300.1 1998-1740 20170222b2017####ek#y0engy0150####ca RUS RU Assessment of the Level of Abstractness of Material Statement of in Natural Sciences School Textbooks Journal article Moscow INFRA-M Academic Publishing LLC. 2017 5 с. Journal article local Mayer R. V. naukaru.ru