Nikolai Nikolaevich Dobrovol’skii
Tula State University, Tula State L. N. Tolstoy Pedagogical University
Russian Federation

candidate of physical and mathematical sciences, associate Professor of the department of applied mathematics and computer science, associate Professor of the department of algebra, mathematical analysis and geometry

Irina Yuryevna Rebrova
Tula State L. N. Tolstoy Pedagogical University
Russian Federation

candidate of physical and mathematical Sciences, associate professor, dean of the faculty of mathematics, physics and computer science

Nikolai Mihailovich Dobrovol’skii
Tula State L. N. Tolstoy Pedagogical University
Russian Federation

doctor of physical and mathematical sciences, professor, head of the department of algebra, mathematical analysis and geometry