<bdi><a href="//commons.wikimedia.org/wiki/Category:Carl_Ludwig_Hummel_de_Bourdon" title="Category:Carl Ludwig Hummel de Bourdon">Carl Ludwig Hummel de Bourdon</a>
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<a rel="nofollow" class="external text" href="https://www.dorotheum.com/auktionen/aktuelle-auktionen/kataloge/list-lots-detail/auktion/11658-master-drawings-prints-before-1900-watercolours-miniatures/lotID/182/lot/2021850-carl-ludwig-hummel-de-bourdon.html">Palais Dorotheum, 30 March 2016, Lot Nr. 182</a>