**4. Conclusions**

In the present paper, the analogy of the Saint-Venant principle is established for the generalized solution of the third order pseudoelliptical type equation. Furthermore, uniqueness theorems are obtained for solutions of the first boundary value problem in classes of functions increasing in infinity depending on the geometric characteristics of the domain *Q* = *D* × Ω × (0, *<sup>T</sup>*), were *D* ⊂ <sup>R</sup>*<sup>n</sup>*+ = {*y* : *y*1 > <sup>0</sup>}, Ω is bounded domain. Boundary value problems for the third order pseudoelliptical type equations in bounded domains were considered in [13].

The main goal of our research on these problems consists of the following parts:


The first part of our research on these problems is given in this paper. The remaining two parts will be studied in the future, which will be performed on the basis of this paper. Therefore, the results of this article are necessary and relevant for further qualitative research to solve third-order equations in the vicinity of irregular boundary points.

**Author Contributions:** Conceptualization, methodology, validation, formal analysis, investigation A.R.K.; validation, formal analysis, D.S. All authors have read and agreed to the published version of the manuscript.

**Funding:** The project is funded by the Institute of Technology and Business in Ceské Budˇ ˇ ejovice, gran<sup>t</sup> numbers: IGS 8210-004/2020 and IGS 8210-017/2020.

**Conflicts of Interest:** The authors declare no conflict of interest.
