SensEURCity: A multi-city air quality dataset collected for 2020/2021 using open low-cost sensor systems oleh Martine Van Poppel, Philipp Schneider, Jan Peters, Sinan Yatkin, Michel Gerboles, Christina Matheeussen, Alena Bartonova, Silvije Davila, Marco Signorini, Matthias Vogt, Franck René Dauge, Jøran Solnes Skaar, Rolf Haugen