A preliminary discussion of a general framework for the treatment of pattern-recognition problems. The authors define "fuzzy" set, then show how this may be used in a sequential experimental procedure to ascertain whether a symbol is a member of a particular set or not.
Bellman, Richard Ernest, Robert E. Kalaba, and Lotfi A. Zadeh, Abstraction and Pattern Classification. Santa Monica, CA: RAND Corporation, 1964. https://www.rand.org/pubs/research_memoranda/RM4307.html. Also available in print form.
Bellman, Richard Ernest, Robert E. Kalaba, and Lotfi A. Zadeh, Abstraction and Pattern Classification, Santa Monica, Calif.: RAND Corporation, RM-4307-PR, 1964. As of September 08, 2021: https://www.rand.org/pubs/research_memoranda/RM4307.html