Ruuskanen, J., Tuch, T., Ten Brink, H., Peters, A., Khlystov, A. Y., Mirme, A., Kos, G., Brunekreef, B., Wichmann, H., Buzorius, G. (2001). Concentrations of ultrafine, fine and PM 2.5 particles in three European cities, Atmospheric Environment, 35 (21), 3729-3738, Pergamon