Fingerprints of the urban particle number size distribution in Helsinki, Finland : Local versus regional characteristics - Hussein, Tareq; Mølgaard, Bjarke; Hannuniemi, Hanna; Martikainen, Jyrki; Järvi, Leena; Wegner, Tobias; Ripamonti, Giovanna; Weber, Stephan; Vesala, Timo; Hämeri, Kaarle (Boreal Environment Publishing Board, 2017)