Pekkanen, J., Timonen, K., Tiittanen, P., Vallius, M., Lanki, T., Sinkko, H., Ruuskanen, J., Mirme, A., Kulmala, M., Vanninen, E. (2000). Ultra : Exposure and risk assessment for fine and ultrafine particles in ambient air : Study manual and data book, 153 p., National Public Health Institute: Helsinki, Finland