@Article{schaefer:model-checking-uml,
  author = 	 {Timm Sch{\"a}fer and Alexander Knapp and Stephan Merz},
  title = 	 {Model checking {UML} state machines and collaborations},
  journal = 	 {Electronic Notes in Theoretical Computer Science},
  year = 	 2001,
  volume =	 55,
  number =	 3,
  pages =	 {13 pages}
}