Yutaka Hata Kyoichi Nakashima Kazuharu Yamato Some Fundamental Properties of Multiple-Valued Kleenean Functions and Determination of Their Logic Formulas. 950-961 1993 42 IEEE Trans. Computers 8 db/journals/tc/tc42.html#HataNY93 http://doi.ieeecomputersociety.org/10.1109/12.238485