Question: What are the ring system  which start with the letter r
SPARQL (Wikidata): SELECT DISTINCT ?sbj ?sbj_label WHERE { ?sbj wdt:P31 wd:Q28951811 . ?sbj rdfs:label ?sbj_label . FILTER(STRSTARTS(lcase(?sbj_label), 'r')) . FILTER (lang(?sbj_label) = 'en') } LIMIT 25