Lawrence Peter Belluce Antonio di Nola Brunella Gerla The Logic of Perfect MV-algebras. 195-199 2007 EUSFLAT Conf. (2) http://www.eusflat.org/publications/proceedings/EUSFLAT_2007/papers/Gerla_Brunella_(74).pdf conf/eusflat/2007-2 db/conf/eusflat/eusflat2007-2.html#BelluceNG07