%0 Journal Article
%A E. I. Znak
%T Operator $Af = f\circ\varphi-f$ in tasks of mathematical competitions
%J Matematičeskoe obrazovanie
%D 2021
%P 23-30
%V 97
%N 1
%I mathdoc
%U http://geodesic.mathdoc.fr/item/MO_2021_97_1_a4/
%G ru
%F MO_2021_97_1_a4