1. L. Alberucci, A. Facchini, The modal μ-calculus hierarchy over restricted classes of transition systems. The Journal of Symbolic Logic (in press)
2. Modal languages and bounded fragments of predicate logic;Andréka;Journal of Philosophical Logic,1998
3. Modal Logic;Blackburn,2001
4. G. D’Agostino, G. Lenzi, On the μ-calculus over transitive and finite transitive frames, Preprint, 2008
5. A. Dawar, M. Otto, Modal characterisation theorems over special classes of frames, in: Proceedings of 20th IEEE Symposium on Logic in Computer Science, LICS’05, 2005, pp. 21–30