Systematically Monitoring Social Media: The case of the German federal election 2017. - Sebastian Stier; Arnim Bleier; Malte Bonart; Fabian Mörsheim; Mahdi Bohlouli; Margarita Nizhegorodov; Lisa Posch; Jürgen Maier; Tobias Rothmund; Steffen Staab (CoRR, 2018)