(C) Øyvind Stavdahl.

These illustrations are shared under the CC BY-NC-SA 4.0 license (details at https://creativecommons.org/licenses/by-nc-sa/4.0/). 

In short, you are free to:
   Share — copy and redistribute the material for non-commercial purposes in any medium or format
   Adapt — remix, transform, and build upon the material

Under the following terms:
   Attribution — You must give appropriate credit, provide a link to the license, and indicate if changes were made . You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use.
   NonCommercial — You may not use the material for commercial purposes .
   ShareAlike — If you remix, transform, or build upon the material, you must distribute your contributions under the same license as the original.

For inquiries about commercial use, please contact oyvind.stavdahl@ntnu.no.