Question: When was upgrading and greening in ward 49 paid?
SPARQL:
select distinct(?date) from <http://linkedspending.aksw.org/pbw-ct> { ?obs qb:dataSet ls:pbw-ct. ?obs lso:pbw-ct-Category <https://openspending.org/pbw-ct/Category/upgrading-and-greening-in-ward-49>. ?obs lso:refDate ?date. }