Question: Which is the door that was commissioned by Frederick William II of Prussia and starts with the letter b?
SPARQL (Wikidata): SELECT DISTINCT ?sbj ?sbj_label WHERE { ?sbj wdt:P31 wd:Q36794 . ?sbj wdt:P88 wd:Q152229 . ?sbj rdfs:label ?sbj_label . FILTER(STRSTARTS(lcase(?sbj_label), 'b')) . FILTER (lang(?sbj_label) = 'en') } LIMIT 25