what is the {start time} for {Burgas} has {head of government} as {Dimitar Nikolov} ?
On what date did Dimitar Nikolov become head of government of Burgas?
When did Dimitar Nikolov become head of government of Burgas?
SELECT ?l WHERE { ?c property:head_of_government resource:Dimitar_Nikolov . resource:Burgas property:head_of_government ?c . ?c property:start_time ?l }
select distinct ?value  where {
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> <http://wikidata.dbpedia.org/resource/Q6509> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.wikidata.org/entity/P6> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> <http://wikidata.dbpedia.org/resource/Q224746> .
?statement <http://www.wikidata.org/entity/P580> ?value. 
} 

SELECT ?value WHERE { wd:Q6509 p:P6 ?s . ?s ps:P6 wd:Q224746 . ?s pq:P580 ?value}