SELECT ?proceedings (COUNT(DISTINCT ?paper) as ?number_of_papers)
WHERE{
VALUES ?volume_number {"3262"}
?proceedings wdt:P31 wd:Q1143604;
wdt:P179 wd:Q27230297;
p:P179/pq:P478 ?volume_number.
?paper wdt:P31 wd:Q13442814;
wdt:P1433 ?proceedings.
}
GROUP BY ?proceedings