[1] R. Jiroušek: Bayes decision functions realized by sequential questionnaires. Trans. Eight Prague Conf. Inform. Theory etc., Vol. C. Academia, Prague 1979, pp. 187-202. MR 0557718

[2] J. R. Shoenfield: Mathematical Logic. Addison-Wesley Publ.Comp., New York 1967 (Russian translation: Nauka, Moscow 1975). MR 0225631 | Zbl 0155.01102