Detecting neutral particles below 3 nm: Calibration of UF-02 proto CPC and first results from Hyytiälä - Riipinen, Ilona; Sipilä, Mikko; Petäjä, Tuukka; Mordas, Genrik; Manninen, H.; Hirsikko, Anne; Hämeri, Kaarle; Kulmala, Markku (Proceedings of BACCI, NECC and FCoE activities 2005 : book B, 2006)