How to find the owner e-mail of the Google document
1. Open a document in Google, for example https://drive.google.com/file/d/1e8IhYxkmpTGE32vutY2EHK4BzqY60r-B/view
2. Now go here (From the same account from which the file was viewed)
3. On the site, find the necessary document, click on it and open the document properties
4. Point the cursor at the owner's name