<a href="//commons.wikimedia.org/wiki/User:Grochim" title="User:Grochim">Grochim</a>
CC BY-SA 3.0
self-made, see <a rel="nofollow" class="external autonumber" href="https://books.google.de/books?id=rcpMjXZEUJoC&amp;printsec=frontcover#PPA175,M1">[1]</a>