The following files originate from the Ana Cardoso Cachopo's Homepage:
[http://ana.cachopo.org/datasets-for-single-label-text-categorization]
    * 20ng-test-all-terms.txt
    * 20ng-train-all-terms.txt
    * r8-test-all-terms.txt
    * r8-train-all-terms.txt
    * r52-test-all-terms.txt
    * r52-train-all-terms.txt