%0 Journal Article %A M. V. Tryamkin %T The length and area principle for a function on an abstract surface over a domain of a Carnot group %J Sibirskie èlektronnye matematičeskie izvestiâ %D 2021 %P 1720-1734 %V 18 %N 2 %I mathdoc %U http://geodesic.mathdoc.fr/item/SEMR_2021_18_2_a77/ %G ru %F SEMR_2021_18_2_a77