[Evaluation of the degree of difficulty in learning school subjects among children of grades 2 to 4].
D002648:Child; D004521:Educational Measurement; D006801:Humans; D007802:Language; D007858:Learning / Q000502:physiology*; D008433:Mathematics; D012586:Science; D014455:Ukraine
Otsenka trudnostiuchebnykh predmetov, izuchaemykh vo 2-4kh klassakh shkoly.