1. The estimation of the weight of a finite tree;Trachtenbrot;Sib. Math. Zh.,1964
2. Comparison of complexities of realization of Boolean functions by finite automata and Turing Machines (in Russian);Breitbart;Dokl. Akad. Nauk SSSR,1968
3. Error detecting and error correcting codes;Hamming;Bell System Tech. J.,1950
4. Estimates of weight of finite automaton;Grinberg;Problemy Peredache Informacii (Russian),1970