Barbara Paech

Barbara Paech: On the Role of Activity Diagrams in UML, UML'98: Beyond the Notation - International Workshop (Preliminary Proceedings), 1998, (BibTeX entry).
Barbara Paech: On the Role of Activity Diagrams in UML: A User Task Centered Development Process for UML, UML'98: Beyond the Notation - International Workshop (Final Proceedings), 1998, (BibTeX entry).
Ruth Breu, Ursula Hinkel, Christoph Hofmann, Cornel Klein, Barbara Paech, Bernhard Rumpe, Veronika Thurner: Towards a Formalization of the Unified Modeling Language, Springer, 1997, (BibTeX entry).

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