Seung Mo Cho Hyung-Ho Kim Sung Deok Cha Doo-Hwan Bae A semantics of sequence diagrams. 125-130 2002 84 Inf. Process. Lett. 3 http://dx.doi.org/10.1016/S0020-0190(02)00270-3 db/journals/ipl/ipl84.html#ChoKCB02