1. ITU, Z.120, in: O. Haugen (Ed.), Message Sequence Charts (MSC), ITU-T, Geneva, 1999, p. 126
2. ITU, Z.100, in: R. Reed (Ed.), Recommendation Z.100: ITU Specification and Description Language, ITU, Geneva, 1999, p. 300
3. ISO, ISO 9646-3, in: The Tree and Tabular Combined Notation (TTCN), ISO/IEC JTC 1/SC 21, 1991
4. J. Grabowski, E. Rudolph, Putting extended sequence charts to practice, in: SDL '89: The Language at Work, SDL Forum 1989, Lisbon, North-Holland, Amsterdam, 1989
5. ITU, Z.120 Annex B, in: S. Mauw et al. (Eds.), Formal Semantics of Message Sequence Charts, ITU-T, Geneva, 1998, p. 76