<https://www.csarmento.uminho.pt/site/api/mapping_markers/375>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<http://omeka.org/s/vocabs/module/mapping#Marker>
<https://www.csarmento.uminho.pt/site/s/postal-ilustrado/item/153766>