@article{Knapp1999,
  author    = {Alexander Knapp},
  title     = {A formal semantics for UML interactions},
  journal   = {Lecture Notes in Computer Science},
  volume    = {1723},
  pages     = {116 -- 130},
  doi       = {10.1007/3-540-46852-8_9},
  year      = {1999},
}