What is {head coach} of {Rafael Nadal} that is {start time} is {1990-0-0} ?
Who was Rafael Nadal's head coach starting in 1990?
SELECT ?obj WHERE { wd:Q10132 p:P286 ?s . ?s ps:P286 ?obj . ?s pq:P580 ?x filter(contains(YEAR(?x),'1990')) }
select distinct ?obj  where {
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> <http://wikidata.dbpedia.org/resource/Q10132> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.wikidata.org/entity/P286> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> ?obj .
?statement <http://www.wikidata.org/entity/P580> <1990-0-0>
} 

in 1990 who was Rafael Nadal's head coach?