Kalita, E. A. (2002). Morrey Regularity of Solutions of Nonlinear Elliptic Systems of Arbitrary Order with Restrictions on the Modulus of Ellipticity. Ukrains’kyi Matematychnyi Zhurnal, 54(11), 1452-1466. https://umj.imath.kiev.ua/index.php/umj/article/view/4184