Get all datasources currently captured in WikiPathways

Statement: 
Get all datasources currently captured in WikiPathways
A limit of $number$ (e.g.10)
Query: 
prefix wp: <http://vocabularies.wikipathways.org/wp#> prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> prefix dcterms: <http://purl.org/dc/terms/> SELECT DISTINCT ?datasource WHERE { ?concept dc:source ?datasource } Limit ??number