query: SELECT ?item ?itemLabel ?series ?seriesLabel ?previous ?previousLabel ?next ?nextLabel WHERE {
    ?item wdt:P31 wd:Q21191270 .
    MINUS {?item wdt:P155 ?previous }. 
    MINUS { ?item wdt:P156 ?next } . 
    OPTIONAL { ?item wdt:P179 ?series } . 
    SERVICE wikibase:label { bd:serviceParam wikibase:language "en,es" . }
    } ORDER BY ?seriesLabel