<bdi><a href="https://en.wikipedia.org/wiki/en:Carl_Hummel" class="extiw" title="w:en:Carl Hummel"><span title="German painter (1821-1907)">Carl Hummel</span></a>
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<a rel="nofollow" class="external text" href="https://www.lempertz.com/de/kataloge/lot/1087-2/1515-carl-maria-nicolaus-hummel.html">Lempertz, Köln, Auktion 1087, 20.05.2017, Lot 1515</a>