Robert L. Probert Ostap Monkewich TTCN: The International Notation for Specifying Tests of Communcations Systems. 417-438 1992 23 Comput. Networks ISDN Syst. 5 db/journals/cn/cn23.html#ProbertM91 https://doi.org/10.1016/0169-7552(92)90015-I