1. Zum Hilbertschen Aufbau der reellen Zahlen
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3. [K] Introduction to Metamathematics. Van Nostrand, Princeton, N.J., 1952, 10 + 550 pp.
4. [KR] and A Universal Two-Way Automaton, to appear in Archiv f. math. Logik.
5. [M] Linear Bounded Automata. WADD technical Note 60–165, Univ. Pennsylvania Report No. 60–22, June 1960.