query: SELECT ?item ?value WHERE
  {
    ?item p:P973/ps:P973 ?value .
    
    FILTER( REGEX(REPLACE(STR(?value), "%20", " "), "^(https?://www2?\\.culture\\.gouv\\.fr/public/mistral/joconde_fr\\?ACTION=CHERCHER&FIELD_1=REF&VALUE_1=([0-9A-Z]{11}))$") )
  }