+<!-- There are also dcq:created and dcq:modified dc:date subProperties -->
+<rdf:Property rdf:ID="firstVersion">
+ <rdfs:comment>Any additional information about the first version of the
+mathematical resource</rdfs:comment>
+ <rdfs:subPropertyOf rdf:resource="&dcns;description"/>
+ <rdfs:domain rdf:resource="#MathResource"/>
+ <rdfs:range rdf:resource="&xschemans;string"/>
+</rdf:Property>
+
+<rdf:Property rdf:ID="modified">
+ <rdfs:comment>Any additional information about the modified version of the
+mathematical resource</rdfs:comment>
+ <rdfs:subPropertyOf rdf:resource="&dcns;description"/>
+ <rdfs:domain rdf:resource="#MathResource"/>
+ <rdfs:range rdf:resource="&xschemans;string"/>
+</rdf:Property>
+