query: #defaultView:Timeline
  SELECT ?mayor ?mayorLabel ?start ?end
  WHERE {
   SERVICE wikibase:label { bd:serviceParam wikibase:language "[AUTO_LANGUAGE],en". }
   ?mayor wdt:P39 wd:Q30185.
   ?mayor p:P39 ?of.
   ?of pq:P642 wd:Q13360.
   ?of pq:P580 ?start.
   OPTIONAL {
   ?of pq:P582 ?end
   }
  }
  ORDER BY ?start