<anchor xmlns="http://www.tei-c.org/ns/1.0" xml:id="id_docs-internal-guid-618ed3ca-7fff-6812-7416-dc554223b7cb" />The decrease of our F1-score alone wasn‘t a great surprise, as the addition of new data is expected to increase diversity within groups and complicates classification. But two observations were irritating: First, we noticed classification results were improved when we included stopwords. Usually removing stopwords improves classification performance (Toman et al. 2006; Gonzales and Quaresma 2014). As most stopwords are typical function words which are used in stylometric research, this indicated that authorship information was used in the classification. Secondly, we noticed strong fluctuations between cross-validation folds, which seemed to indicate a very uneven class distribution.