%0 Journal Article
%A S. J. Bilchev
%T The linearity of systems of two first order partial differential equations
%J Izvestiâ vysših učebnyh zavedenij. Matematika
%D 1974
%P 3-14
%N 1
%I mathdoc
%U http://geodesic.mathdoc.fr/item/IVM_1974_1_a0/
%G ru
%F IVM_1974_1_a0