@article{Ptashnik_Symotyuk_2003, title={Multipoint Problem with Multiple Nodes for Partial Differential Equations}, volume={55}, url={https://umj.imath.kiev.ua/index.php/umj/article/view/3914}, abstractNote={We establish conditions for the existence and uniqueness of a solution of a problem with multipoint conditions with respect to a selected variable <em class="a-plus-plus">t</em> (in the case of multiple nodes) and periodic conditions with respect to <em class="a-plus-plus">x</em> <sub class="a-plus-plus">1</sub>,..., <em class="a-plus-plus">x</em> <sub class="a-plus-plus">p</sub> for a nonisotropic partial differential equation with constant complex coefficients. We prove metric theorems on lower bounds for small denominators appearing in the course of the solution of this problem.}, number={3}, journal={Ukrainsâ€™kyi Matematychnyi Zhurnal}, author={Ptashnik, B. I. and Symotyuk, M. M.}, year={2003}, month={Mar.}, pages={400-413} }