1. Booch, G., Rumbaugh, J., Jacobson, I.: The Unified Modeling Language User Guide. Addison-Wesley, Upper Saddle River (2005)
2. Tseng, F., Chen, C.: Enriching the class diagram concepts to capture natural language semantics for database access. Data & Knowledge Engineering 67, 1–29 (2008)
3. Ilieva, M.: Graphical notation for natural language and knowledge representation. In: SEKE 2007, pp. 361–367 (2007)
4. Ilieva, M., Boley, H.: Representing textual requirements as graphical natural language for UML diagram generation. In: SEKE 2008, pp. 478–483 (2008)
5. Bryan, B., Lee, B.: Two-level Grammar as an Object-Oriented Requirements Specification. In: 35th Hawaii Int. Conf. System Sciences (2002)