1. Towards the expressive power of natural language;Sowa,1990
2. Extending the conceptual graph model for differentiating temporal and nontemporal knowledge;Moulin,1990
3. Conceptual Structures: Information Processing in Mind and Machine;Sowa,1984
4. Elements of Symbolic Logic;Reichenbach,1947
5. Temporal Structure in Sentence and Discourse,1986