From quantity to quality
T.A. Henzinger, O. Kupferman, in:, Proceedings of the 5th International Workshop on Hybrid and Real-Time Systems, Springer, 1997, pp. 48–62.

Robust timed automata
V. Gupta, T.A. Henzinger, R. Jagadeesan, in:, Proceedings of the 5th International Workshop on Hybrid and Real-Time Systems, Springer, 1997, pp. 331–345.