Beginner warning :) I am exploring the Eurovoc European multilingual database of concept keywords.

SPARQL endpoint can be accessed at http://publications.europa.eu/webapi/rdf/sparql

I wish to find all terms in it only for the Italian language and for each term I want to see the prefLabel but also if there are any alternate forms of that concept (altLabel).

My current query is:

select ?s ?plabel ?alabel where {
?s a skos:Concept .
?s skos:prefLabel ?plabel .
?s skos:altLabel ?alabel .
 FILTER (langMatches(lang(?plabel),"it"))
} limit 100

and it properly returns the prefLabel concepts but the altLabels are not related to them. What's wrong? Thanks a lot.