Google. As much as I'd like to use other search engines, their search results are all severely lacking and not adequate for my needs (often pertaining to research) and they're generally not as great on the multilingual front or in searching pdfs.
I also have some keywords set up in my browser so I can directly search sites I use (e.g. Wikipedia).
Are the question marks around the northern route vs southern route addressed in the study? Or are they just assumptions?