"FWIW I found this https://files.eric.ed.gov/fulltext/EJ1061970.pdf" with no context (apart from being in this thread) and no discussion of its content and/or relevance is a red-flag to many forum users.
PDF files can be vectors for malware. Sites can be, and have been, hacked and malicious files put up.

I think Jack was reasonable in his response. You still haven't explained why it's worth the time and the risk.