[1] Bečvář J.: Real-Time and Complexity Problems in Automata Theory. Kybernetika 1 (1965), 6, 475-497.
[2] Fischer P. C.: Multi-tape and infinite-state automata. International Colloquium on Algebraic Linguistics and Automata Theory, 1964, Jerusalem, Israel.
[3] Глушков B. M.: 
Синтез цифровых автоматов. Физматгиз, Москва 1962. 
Zbl 1005.68507[4] Hartmanis J., Lewis P. M., Stearns R. E.: 
Classifications of Computations by time and memory requirements. IFIP Congress, New York 1965. 
Zbl 0203.16401[5] Hartmanis J., Stearns R. E.: 
On the computational complexity of algorithms. Trans. Amer. Math. Soc. 117 (1965), 285-306. 
MR 0170805 | 
Zbl 0131.15404[7] Yamada H.: 
Real-time computation and recursive functions not real-time computable. IRE Trans. on Electronic Computers EC-11 (1965), 753-760. 
MR 0152161[8] Yamada H.: Counting by a class of growing automata. PhD Thesis, Moore School of Elect. Eng., University of Pennsylvania, 1960.