Looks like it's covertly suggested in #5

    5. Install Browser Extensions

    Browser extensions can help you check the web for free versions of academic articles. 
    The Unpaywallbrowser extension gathers content from more than 50,000 journals and open-access repositories worldwide. 
    The Open Access Button searches “millions of articles” from sources that include “all of the aggregated repositories 
    in the world, hybrid articles, open access journals, and those on authors’ personal pages,” according to its website.

    If the Open Access Button does not find free versions of the articles you’re looking for, it will contact the authors and
    ask them to share their work by putting it into an open access repository.