The illustrations above that can be downloaded are licensed under a CC BY-NC-SA 4.0 license. It means they are free to use for non-commercial purposes, such as scientific publications. Please credit me when using them, with my name (Ben Kawam), and additionally — when possible —, with the url of this website (benkawam.github.io). The illustrations that cannot be downloaded, however, are under full copyright, and cannot be used without permission.