It's about time: Real-time logics reviewed
T.A. Henzinger, in:, Proceedings of the 9th Interantional Conference on Concurrency Theory, Schloss Dagstuhl - Leibniz-Zentrum für Informatik, 1998, pp. 439–454.

Alternating refinement relations
R. Alur, T.A. Henzinger, O. Kupferman, M. Vardi, in:, Proceedings of the 9th Interantional Conference on Concurrency Theory, Schloss Dagstuhl - Leibniz-Zentrum für Informatik, 1998, pp. 163–178.