Vinzenz Katzler, Public domain, via Wikimedia Commons
Alessandro Marchesini, Public domain, via Wikimedia Commons
Photograph taken by Mark A. Wilson (Department of Geology, The College of Wooster).[1], Public domain, via Wikimedia Commons
Stéphane Passet (1875-after 1930), on behalf of Albert Kahn (1860-1940), Public domain, via Wikimedia Commons
Harry Clarke, Public domain, via Wikimedia Commons