The data that they used has now been released as the Google NGrams dataset, and so we can use the data to replicate and extend some of their work.
Idatha ayisebenzisayo manje ikhishwe njengedatha yedatha ye-Google NGrams, ngakho-ke singasebenzisa idatha ukuze iphinde iphinde iphinde isandise enye yomsebenzi wayo.