1. M. O. Rabin, D. Scott, “Finite Automata and their Decisions Problems”, IBM J. Res. and Dev. 3 (1959) 114–125. (Reprinted in [Mo64] 63–91.)
2. M. L. Tsetlin, “Non-primitive Circuits” (in Russian) Problemy Kibernetiki 2 (1959).
3. J. R. Büchi, “On a Decision Method in Restricted Second-Order Arithmetic”, Proc. Internat. Cong. on Logic, Methodol. and Philos. of Sci., 1960, 1–11 (Stanford Univ. Press, 1962).
4. M. O. Rabin, “Decidability of Second-Order Theories and Automata on Infinite Trees”, Trans. Amer. Math. Soc. 141 (1969) 1–35.
5. M. O. Rabin, Automata on Infinite Objects and Church's Problem. Amer. Math. Soc., 1972.