Question: Tell me which structural class of chemical compounds start with the letter u.
SPARQL (Wikidata): SELECT DISTINCT ?sbj ?sbj_label WHERE { ?sbj wdt:P31 wd:Q47154513 . ?sbj rdfs:label ?sbj_label . FILTER(STRSTARTS(lcase(?sbj_label), 'u')) . FILTER (lang(?sbj_label) = 'en') } LIMIT 25