1. Freud, Sigmund: Jokes and Their Relation to the Unconscious, 1905, (transl. Strachey) Standard Edition, vol. 8, Hogarth Press, 1957.
2. Doyle, Jon: Truth Maintenance Systems for Problem Solving, M.I.T., Artificial Intelligence Laboratory, AI/TR-419, January 1978.
3. Kornfeld, William A.: Using Parallel Processes for Problem Solving, M.I.T., Artificial Intelligence Laboratory, AI Memo 561, Cambridge, Ma., December 1979.
4. Korzybski, Alfred: Science and Sanity, Science Press, Lancaster, Pa., 1941.
5. Minsky, Marvin: A Framework for Representing Knowledge, M.I.T., Artificial Intelligence Laboratory, AI Memo 306, Cambridge, Ma., June 1974.