Question: How much external debt did rivers have in 2010?
SPARQL:
select sum(xsd:decimal(?amount)) as ?sum from <http://linkedspending.aksw.org/external-debts> { ?obs qb:dataSet ls:external-debts. ?obs lso:external-debts-to <https://openspending.org/external-debts/to/rivers>. ?obs lso:external-debts-amount ?amount. ?obs lso:refYear ?year. filter(year(?year)=2010) }