query: embed.html#SELECT 
    ?p ?pLabel 
    ?recency ?recencyunitLabel
    ?pDescription
    ?SingleBestValueConstraint ?SingleValueConstraint
  WHERE
  {
  	?p wikibase:propertyType wikibase:Quantity .
      ?p p:P2302 [ ps:P2302 wd:Q21510856 ; pq:P2306 wd:P585 ] 
  	OPTIONAL { ?p p:P1552 [ ps:P1552 wd:Q102173107 ; pq:P2047 ?recency ; pqv:P2047 / wikibase:quantityUnit ?recencyunit ] }
  	OPTIONAL { ?p wdt:P2302 wd:Q19474404 . BIND("y" as ?SingleValueConstraint ) }  	
      OPTIONAL { ?p wdt:P2302 wd:Q52060874 . BIND("y" as ?SingleBestValueConstraint ) }  
      SERVICE wikibase:label { bd:serviceParam wikibase:language "[AUTO_LANGUAGE],en". }
  }
  ORDER BY (?p = wd:P1082) (BOUND(?recency)) (!BOUND(?SingleBestValueConstraint))