How many {author} are to/by {Carl Chun} ?
Carl Chun was written by how many authors?
How many authors are written the {Carl Chun} ?
SELECT ( COUNT ( ?l ) AS ?q ) { ?l property:author resource:Carl_Chun }
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/P50> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> http://wikidata.dbpedia.org/resource/Q62747 .
} 

SELECT (COUNT(?sub) AS ?value ) { ?sub wdt:P50 wd:Q62747 }
4