<a href="https://en.wikipedia.org/wiki/Bonn" class="extiw" title="en:Bonn">Bonn</a>, Beethoven-Gymnasium school, inscription for <a href="https://en.wikipedia.org/wiki/Hermann_von_Helmholtz" class="extiw" title="en:Hermann von Helmholtz">Hermann von Helmholtz</a>
<a href="https://de.wikipedia.org/wiki/User:Sir_James" class="extiw" title="de:User:Sir James">Sir James</a>
CC BY-SA 3.0 de
<span class="int-own-work" lang="en">Own work</span>