Henzinger, Thomas A, Orna Kupferman, and Ritankar Majumdar. “On the Universal and Existential Fragments of the Mu-Calculus.”https://doi.org/10.1007/3-540-36577-X_5__In Proceedings of the 9th International Conference on Tools and Algorithms for the Construction and Analysis of Systems , 2619:49–64. Springer, 2003.https://doi.org/10.1007/3-540-36577-X_5 .