Thomas Gehrke

Thomas Gehrke, Ursula Goltz, Heike Wehrheim: Zur semantischen Analyse der dynamischen Modelle von UML mit Petri-Netzen, 6th Symposium on Development and Operation of Complex Automation Systems, 1999, (BibTeX entry).
Thomas Firley, Michaela Huhn, Karsten Diethers, Thomas Gehrke, Ursula Goltz: Timed Sequence Diagrams and Tool-Based Analysis A Case Study, Second International Conference on the Unified Modeling Language: UML'99, 1999, (BibTeX entry).
Thomas Gehrke, Ursula Goltz, Heike Wehrheim: The Dynamic Models of UML: Towards a Semantics and its Application in the Development Process, 1998, (BibTeX entry).

dblp: Computer Science Bibliography (University of Trier, Germany). (Note that this does not always work due to different naming schemes.)