 The relationship between fusion and algebraic fibring deserves some comments. When restricted to modal propositional logics, fusion is a particular case of algebraic fibring in the category of interpretation systems, where logics are presented through ordered algebras: it is enough to consider interpretation systems defined over power set algebras induced by Kripke models. At the syntactical level, fusion is also a particular case of algebraic fibring in the category of Hilbert calculi, in the realm of propositional signatures. As much as first-order modal logics are concerned, the approaches diverge, mainly because there are different semantical accounts for treating first-order modalities. For instance, the semantical approach to modal first-order logics by Sernadas et al. 2002a in the context of algebraic fibring differs from that of Kracht and Kutz (2002) in the context of fusion.