ВasM. O., and LavrenyukS. P. 1996. “On the Uniqueness of a Solution of the Fourier Problem for a System of Sobolev-gal’pern Type”. Ukrains’kyi Matematychnyi Zhurnal 48 (1), 124-28. https://umj.imath.kiev.ua/index.php/umj/article/view/5370.