What are the start and end dates of Greg Nickels as mayor of Seattle?
SELECT ?value1 ?value2 WHERE { wd:Q5083 p:P6 ?s . ?s ps:P6 wd:Q330519 . ?s pq:P2032 ?value1 . ?s pq:P2031 ?value2 }
seattle: Q5083 greg nickels: Q330519