“…However, researchers proposed several domain adaptation techniques by using the unlabeled test data to obtain better performance [5,14,16,25,37]. Interestingly, some recent works [13,18] indicate that string kernels can yield robust results in the cross-domain setting without any domain adaptation. In fact, methods based on string kernels have demonstrated impressive results in various text classification tasks ranging from native language identification [22][23][24]36] and authorship identification [34] to dialect identification [4,18,21], sentiment analysis [13,35] and automatic essay scoring [7].…”