Complex sentence: The second Free Exhibition opened on 2 April 1898 in the Ateneum Art Museum's hall, once again organized by Sigurd Wettenhovi-Aspa and Torsten Wasastjerna.
Split into simpler sentences: The second Free Exhibition opened on 2 April 1898 in the Ateneum Art Museum's hall. Organizers were yet again Sigurd Wettenhovi-Aspa and Torsten Wasastjerna.