Derivative work from <a href="//commons.wikimedia.org/wiki/File:Evolution-des-wissens.jpg" title="File:Evolution-des-wissens.jpg">File:Evolution-des-wissens.jpg</a>
<a href="//commons.wikimedia.org/wiki/User:Ldorfman" title="User:Ldorfman">Ldorfman</a> - According to a work of Johanna Pung made for Wikimedia Deutschland
CC BY-SA 3.0
<span class="int-own-work" lang="en">Own work</span>