There are some strange footnotes in text that look like this:

[![strange footnotes](https://i.stack.imgur.com/XBSE7.png)](https://i.stack.imgur.com/XBSE7.png)

in text:

[![enter image description here](https://i.stack.imgur.com/zVP9o.png)](https://i.stack.imgur.com/zVP9o.png)

At the university, we were given a task to remake in LaTeX a very old Soviet book on mathematical analysis by Grigoriy Fichtenholz. So I found these footnotes in the text. And they are everywhere. And I don't know what to do with them. Is there any command to change style of `\footnote`? Or there is some special way?