Pierangelo Miglioli Ugo Moscato Mario Ornaghi Avoiding duplications in tableau systems for intuitionistic logic and Kuroda logic. 1997 5 Logic Journal of the IGPL 1 http://www3.oup.co.uk/igpl/Volume_05/Issue_01/#miglioli db/journals/igpl/igpl5.html#MiglioliMO97