Matthias Baaz Agata Ciabattoni Christian G. Fermüller Monadic Fragments of Gödel Logics: Decidability and Undecidability Results. 77-91 2007 conf/lpar/2007 LPAR http://dx.doi.org/10.1007/978-3-540-75560-9_8 db/conf/lpar/lpar2007.html#BaazCF07