Relations between Polish and Moscow mathematicians in the first half of the XXth century

The article is devoted to the appearance of the famous Warsaw mathematical School of V. Sierpinski and Lviv School of Functional Analysis of S. Banach. These schools have played an important role in the development of new areas of mathematics in the first half of the 20th century. Particular attention is paid to the interrelations between Polish and Moscow mathematicians in the period between the two world wars. Most of their outstanding results, especially in topology, Moscow scientists published in the newly created Polish mathematical journals. The leaders of the schools constantly maintained close friendly relations, as evidenced by the surviving letters of N. N. Luzin and V. Sierpinsky, P. S. Uryson and K. Kuratovsky, N. K. Bari and A. Rajchman, in which, among others, the organization of mathematical research was discussed.
The participation of Polish scientists in the work of several important mathematical forums held at that time in the USSR was covered: the First Congress of Mathematicians of the USSR in Kharkov (1930), the International Conference on Differential Geometry and Tensor Analysis (Moscow, 1934) and the International Topological Conference (Moscow, 1935). It is noted that in Moscow and in Polish universities in the first half of the 20th century scientific student seminars were starting to work, the themes of which also have indicated the constant interest of both Polish and Moscow mathematicians in their colleagues research.