How many {dissertation submitted to} are to/by {TU Dresden} ?
Who was the dissertation submitted to?
Was the dissertation submitted to TU Dresden?
SELECT ( COUNT ( ?y ) AS ?z ) { ?y property:dissertation_submitted_to resource:TU_Dresden }
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/P4101> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> http://wikidata.dbpedia.org/resource/Q158158 .
} 

SELECT (COUNT(?sub) AS ?value ) { ?sub wdt:P4101 wd:Q158158 }
6