How many {cover artist} are to/by {Carl Barks} ?
How many artists covered Carl Barks work?
SELECT (COUNT(?sub) AS ?value ) { ?sub wdt:P736 wd:Q11941 }
SELECT (COUNT(?sub) AS ?subs ) {
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> ?sub .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.wikidata.org/entity/P736> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> http://wikidata.dbpedia.org/resource/Q11941 .
} 

What is the number of artists that covered Carl Barks work?