%0 Journal Article
%A M. B. Karmanova
%T Two-step sub-Lorentzian structures and graph surfaces
%J Izvestiya. Mathematics 
%D 2020
%P 52-94
%V 84
%N 1
%I mathdoc
%U http://geodesic.mathdoc.fr/item/IM2_2020_84_1_a3/
%G en
%F IM2_2020_84_1_a3