“…Concerning cellular automata with simple structure, many important results have been reported by Kawahara et al [Kawahara (1991), Kawahara et al (1992), Inokuchi and Sato et al (1996)]. Especially, the author has investigated cellular automata with threshold rules and having limit cycles of period length 3 [Sato (1996a), Sato (1996b), Sato (1998), Sato (1999), Inokuchi and Sato (2000)]. As to cellular automata with threshold rules, Shingai reported that period lengths of limit cycles are 4 or less [Shingai (1978)].…”