Buryachenko EA. Conditions of nontrivial solvability of the homogeneous Dirichlet problem for equations of any even order in the case of multiple characteristics without slope angles. Ukr. Mat. Zhurn. [Internet]. 2010May25 [cited 2024May4];62(5):591–603. Available from: https://umj.imath.kiev.ua/index.php/umj/article/view/2890