Zhirnov, O. P.
Article History
Received: 18 March 2020
Revised: 22 March 2020
Accepted: 22 March 2020
First Online: 3 June 2020
Compliance with ethical norms
: This article does not contain description of studies involving humans or animals as research subjects. The author declares no conflict of interest. This study was prepared without financial support.
Free to read: This content has been made available to all.