when did the relationship between Gore Vidal and Howard Austen start?
SELECT ?value1 ?value2 WHERE { wd:Q167821 p:P451 ?s . ?s ps:P451 wd:Q17309157 . ?s pq:P582 ?value1 . ?s pq:P580 ?value2 }
gore vidal: Q167821 howard austen: Q17309157