4 ms·

I assume they are referring to the fact that books older than about 70 years are in the public domain. The rest are protected by copyright and not free.

• ls15 4y ago
  I think so too, but I am referring to this statement: > The overwhelming majority of our knowledge is in the public domain
  • popcube 4y ago
    if we talk about biology, absolutely not, but most of high school students won't finish basic physics, so this make sense in some region