PREFIX dbo: <http://dbpedia.org/ontology/>
PREFIX res: <http://dbpedia.org/resource/>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
SELECT DISTINCT ?uri ?polish ?english
WHERE {
    res:Poland dbo:currency ?uri .
        OPTIONAL { ?uri rdfs:label ?polish. FILTER (lang(?polish) = 'pl') }
        OPTIONAL { ?uri rdfs:label ?english. FILTER (lang(?english) = 'en') }
}