Counts the data sources used in the wheat dataset. Try it [here][10].
PREFIX bk: <http://knetminer.org/data/rdf/terms/biokno/>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
PREFIX bkg: <http://knetminer.org/data/rdf/resources/graphs/>
SELECT DISTINCT ?dataSource (COUNT (DISTINCT ?e) AS ?resources)
FROM bkg:wheat
{