Henzinger, T. A. (1998). It’s about time: Real-time logics reviewed. In Proceedings of the 9th Interantional Conference on Concurrency Theory (Vol. 1466, pp. 439–454). Nice, France: Schloss Dagstuhl - Leibniz-Zentrum für Informatik.https://doi.org/10.1007/BFb0055640 

Alur, R., Henzinger, T. A., Kupferman, O., &; Vardi, M. (1998). Alternating refinement relations. In Proceedings of the 9th Interantional Conference on Concurrency Theory (Vol. 1466, pp. 163–178). Nice, France: Schloss Dagstuhl - Leibniz-Zentrum für Informatik.https://doi.org/10.1007/BFb0055622