Peter Graubmann Ekkart Rudolph HyperMSCs and Sequence Diagrams for Use Case Modelling and Testing. 32-46 http://link.springer.de/link/service/series/0558/bibs/1939/19390032.htm 2000 conf/uml/2000 UML db/conf/uml/uml2000.html#GraubmannR00