As a math teacher in french so-called "Classes préparatoires aux grandes écoles" (see http://en.wikipedia.org/wiki/Grandes_%E9coles) since... 1979, I believe to educational progress by means of free sharing of knowledge. Since September 2013, I give a free access to all my professionnal papers (about 1800 pages) on my website: http://www.mathprepa.fr. Since then, thousands of students from everywhere came and downloaded files which, I hope, are useful to their curriculum.