Question: When did Mobutu Sese Seko become the chairperson of the Organisation of African Unity?
Paraphrase: Mobutu Sese Seko became chairperson of the Organisation of African Unity when?
SPARQL (Wikidata): SELECT ?value WHERE { wd:Q164535 p:P39 ?s . ?s ps:P39 wd:Q19161632 . ?s pq:P580 ?value}