P.S.Aleksandrov and A.N.Kolmogorov, Introduction to the General Theory of Sets and Functions, Gosudarstv. Izdat. Tehn.-Teor. Lit., Moscow–Leningrad, 1948.
2.
S.C.Kleene and E.L.Post, The upper semi-lattice of degrees of recursive unsolvability, Annals of Mathematics. Second Series59(3) (1954), 379–407.
3.
A.Kolmogoroff, Zur Deutung der intuitionistischen Logik, Mathematische Zeitschrift35(1) (1932), 58–65.
4.
A.V.Kuznetsov and B.A.Trakhtenbrot, Investigation of partial recursive operators by means of the theory of Baire space, Doklady Akademii Nauk SSSR105(5) (1955), 897–900.
5.
Y.T.Medvedev, Degrees of difficulty of mass problems, Doklady Akademii Nauk SSSR104(4) (1955), 501–504.
6.
A.A.Muchnik, On the unsolvability of the problem of reducibility in the theory of algorithms, Doklady Akademii Nauk SSSR108(2) (1956), 194–197.
7.
A.A.Muchnik, On the reducibility of problems of solvability of enumerable sets to problems of separability, Izvestiya Akademii Nauk SSSR, Seriya Matematicheskaya29 (1965), 717–724.
8.
E.L.Post, Recursively enumerable sets of positive integers and their decision problems, Bulletin of the American Mathematical Society50(5) (1944), 284–316.
9.
E.D.Stotskii, On the descriptive theory of games, in: Problemy Kibernetiki (Problems of Cybernetics), Vol. 8, Fizmatgiz, Moscow, 1962, pp. 45–54.
10.
B.A.Trakhtenbrot, On recursive separability, Doklady Akademii Nauk SSSR88(6) (1953), 953–956.
11.
B.A.Trakhtenbrot, Tabular representation of recursive operators, Doklady Akademii Nauk SSSR101(3) (1955), 417–420.
12.
V.A.Uspenskii, Gödel’s theorem and the theory of algorithms, Doklady Akademii Nauk SSSR91(4) (1953), 737–740.
