Gunnar Övergaard

Gunnar Övergaard: A Formal Approach to Relationships in The Unified Modeling Language, PSMT - Workshop on Precise Semantics for Software Modeling Techniques, 1998, (BibTeX entry).
Gunnar Övergaard, Karin Palmkvist: A Formal Approach to Use Cases and their Relationships, UML'98: Beyond the Notation - International Workshop (Preliminary Proceedings), 1998, (BibTeX entry).
Gunnar Övergaard, Karin Palmkvist: A Formal Approach to Use Cases and Their Relationships, UML'98: Beyond the Notation - International Workshop (Final Proceedings), 1998, (BibTeX entry).
Gunnar Övergaard: A Formal Approach to Collaborations in the Unified Modeling Language, Second International Conference on the Unified Modeling Language: UML'99, 1999, (BibTeX entry).
Gunnar Övergaard, Karin Palmkvist: Interacting Subsystems in UML, Third International Conference on the Unified Modeling Language: UML 2000, 2000, (BibTeX entry).
Gunnar Övergaard: Formal Specification of Object-Oriented Meta-Modelling, Springer, 2000, (BibTeX entry).

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