1. Ogden, C.K., and Richards, I.A. (1923). The Meaning of Meaning, Harcourt, Brace.
2. Eco, U. (1968). La Struttura Assente, Bompiani.
3. The Physical Symbol Grounding Problem;Vogt;Cogn. Syst. Res.,2001
4. Vogt, P. (2006). Artificial Cognition Systems, IGI Global.
5. Language games for autonomous robots;Steels;IEEE Intell. Syst.,2001