I have bought many e-books in the last months, how do I know if they I have the resale rights of those e-books? Thank you
When you bought it, the person you bought it from would have told you if you were also getting re-sell rights.
Normally if those book got resale right you will receive their resale right license as well and sometimes they also will mention inside the ebooks.
Sometimes there is an "official" document stating that you have resell rights, sometimes it is stated from who you are buying it from. If you can't remember, though, don't sell it.