Franco Montagna G. Michele Pinna Elisa B. P. Tiezzi A Tableau Calculus for Hájek's Logic BL. 241-259 2003 13 J. Log. Comput. 2 http://dx.doi.org/10.1093/logcom/13.2.241 db/journals/logcom/logcom13.html#MontagnaPT03