Question: Who was Rafael Nadal's head coach starting in 1990?
Paraphrase: in 1990 who was Rafael Nadal's head coach?
SPARQL (Wikidata): SELECT ?obj WHERE { wd:Q10132 p:P286 ?s . ?s ps:P286 ?obj . ?s pq:P580 ?x filter(contains(YEAR(?x),'1990')) }