[1] CEĬTIN G. S.: 
Algorithmic operators in constructive metric spaces. Trudy Mat. Inst. Steklov 67 (1962), 295-361; English transl., Amer. Math. Soc. Transl. (2) 64 (1967), 1-80. 
MR 0152426[2] CEĬTIN G. S.: 
On upper bounds of recursively enumerable sets of constructive real numbers. Trudy Mat. Inst. Steklov, 113 (1970), 102-172 = Proc. Steklov Inst. Math. 113 (1970), 119-194. 
MR 0321710[3] DEMUTH O.: 
On constructive pseudonumbers. Comment. Math. Univ. Carolinae 16 (1975), 315-331 (Russian). 
MR 0381955[5] JOCKUSCH C. G., Jr., SOARE R. I.: 
Degrees of members of $\Pi_1^0$ classes. Pacific J. Math. 40 (1972), 605-616. 
MR 0309722[6] KUČERA A.: 
Measure, $\Pi_1^0$-classes and complete extensions of PA. Lecture Notes in Math., vol. 1141, Springer-Verlag, Berlin, 1985, 245-259. 
MR 0820784[7] KUŠNER B. A.: 
Ort coverings of separable sets. Issled. po těorii algorifmov i mat. logike, Vyč. centr AN SSSR, Moskva, 1973, 235-246. 
MR 0337534[8] MARTIN, LÖF P.: 
Notes on Constructive Mathematics. Almquist & Wiksell, Stockholm, 1970.      
MR 0485251