Naumov, P. G. Undecidability of a second-order provability logic with operation of comparison of witnesses. (English. Russian original) Zbl 0826.03010 Mosc. Univ. Math. Bull. 48, No. 3, 13-15 (1993); translation from Vestn. Mosk. Univ., Ser I 1993, No. 3, 14-17 (1993). MSC: 03B45 03B25 03F30 PDFBibTeX XMLCite \textit{P. G. Naumov}, Mosc. Univ. Math. Bull. 48, No. 3, 1 (1993; Zbl 0826.03010); translation from Vestn. Mosk. Univ., Ser I 1993, No. 3, 14--17 (1993)
Nogina, E. Yu. On classes of arithmetical counterparts of modal provability logics. (English. Russian original) Zbl 0711.03002 Mosc. Univ. Math. Bull. 45, No. 1, 31-33 (1990); translation from Vestn. Mosk. Univ., Ser. I 1990, No. 1, 31-33 (1990). Reviewer: S.N.Artemov MSC: 03B45 03F30 03F40 PDFBibTeX XMLCite \textit{E. Yu. Nogina}, Mosc. Univ. Math. Bull. 45, No. 1, 31--33 (1990; Zbl 0711.03002); translation from Vestn. Mosk. Univ., Ser. I 1990, No. 1, 31--33 (1990)