When did Anni-Frid Lyngstad marry Prince Heinrich Ruzzo Reuss of Plauen?
SELECT ?value WHERE { wd:Q201908 p:P26 ?s . ?s ps:P26 wd:Q1208883 . ?s pq:P580 ?value}
anni-frid lyngstad: Q201908 prince heinrich ruzzo reuss of plauen: Q1208883