1. Balzer, R.: An 8-state minimal time solution to the firing squad synchronization problem. Inf. Control 10, 22–42 (1967)
2. Berthiaume, A., Bittner, T., Perković, L., Settle, A., Simon, J.: Bounding the firing synchronization problem on a ring. Theoret. Comput. Sci. 320, 213–228 (2004)
3. Gerken, H.D.: Über Synchronisationsprobleme bei Zellularautomaten. Diplomarbeit, Institut für Theoretische Informatik, Technische Universität Braunschweig, pp. 1–50 (1987)
4. Goto, E.: A minimal time solution of the firing squad problem. Dittoed course notes for Applied Mathematics 298 (with an illustration in color), Harvard University, pp. 52–59 (1962)
5. Kamikawa, N., Umeo, H., Fujita, G.: A class of 4-state array synchronizers. Annual Report for Institute of Informatics, University of Osaka Electro-communication, draft version, (2020) (to appear)