Project(OrderBy(BGP( ?term <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://www.w3.org/2000/01/rdf-schema#Class> .
                     ?term <http://purl.org/dc/terms/source> ?src .
                     ?term <http://www.w3.org/2000/01/rdf-schema#label> ?term_label), (?src)),
        {?term_label, ?src})