Machinelearning papers

I created a folder for machine learning papers and added links to 3 good papers.

Would it be better to add the PDFs, or are the external links a better option?

Below are links to the articles on the journal websites:
Top 10 algorithms in Data Mining - http://link.springer.com/article/10.1007%2Fs10115-007-0114-2
A few useful Things to Know about machine learning - http://dl.acm.org/citation.cfm?id=2347755
Random Forest - http://link.springer.com/article/10.1023%2FA%3A1010933404324