Albert Einstein's signature.  Under United States Copyright Law, signatures are not eligible for copyright, as they are "titles, names...mere variations of typographic ornamentation, lettering, or coloring".(<a rel="nofollow" class="external text" href="https://www.copyright.gov/circs/circ1.html#wnp">see here</a>)
<p>Albert Einstein
</p>
<dl><dd><ul><li>derivative work: <a href="//commons.wikimedia.org/wiki/User:Pbroks13" title="User:Pbroks13">Pbroks13</a> (<a href="//commons.wikimedia.org/wiki/User_talk:Pbroks13" class="mw-redirect" title="User talk:Pbroks13">talk</a>)</li></ul></dd></dl><ul><li><a href="//commons.wikimedia.org/wiki/File:Albert_Einstein_signature.png" title="File:Albert Einstein signature.png">Albert_Einstein_signature.png</a>: Albert Einstein (uploaded to the Commons by <a href="//commons.wikimedia.org/wiki/User:Epson291" title="User:Epson291">Epson291</a>)</li></ul>
<ul><li><a href="//commons.wikimedia.org/wiki/File:Albert_Einstein_signature.png" title="File:Albert Einstein signature.png">Albert_Einstein_signature.png</a></li></ul>