Attribution 4.0 International (CC BY 4.0)

Copyright (c) 2018 Maximilian Ruta 

You are free to:

 - Share — copy and redistribute the material in any medium or format
 - Adapt — remix, transform, and build upon the material for any purpose, even commercially.
   This license is acceptable for Free Cultural Works.

The licensor cannot revoke these freedoms as long as you follow the license terms.