1. Nothing's plenty: The vacuum in modern quantum field theory;Aitchison;Contemporary Physics,1985
2. Cognition, convention, and communication;Bickhard,1980
3. The necessity of possibility and necessity. Review of Piaget's possibility and necessity;Bickhard;Harvard Educational Review,1988
4. Representational content in humans and machines;Bickhard;Journal of Experimental and Theoretical Artificial Intelligence,1993
5. Levels of representationality;Bickhard;Journal of Experimental and Theoretical Artificial Intelligence,1998