Petr Cintula Francesc Esteva Joan Gispert Lluis Godo Franco Montagna Carles Noguera Distinguished algebraic semantics for t-norm based fuzzy logics: Methods and algebraic equivalencies. 53-81 2009 160 Ann. Pure Appl. Logic 1 http://dx.doi.org/10.1016/j.apal.2009.01.012 db/journals/apal/apal160.html#CintulaEGGMN09