[Vershik, A. M.; Pavlov, B. S.; Faddeev, L. D.; McKean, H. P.; Helson, H.; Nikol’skij, N. K.; Vasyunin, V. I.; Sz.-Nagy, B.; Naboko, S. N.; Sakhnovich, L. A.; Clark, D. N.; Douglas, R. G.; Leiterer, J.; Peller, V. V.; Smyth, M. R. F.; West, T. T.; Putnam, C. R.] Studies in linear operators and function theory. 99 Unsolved problems in linear and complex analysis. Chapter 4. Linear operators. (English) Zbl 0543.47001 J. Sov. Math. 26, 2137-2169 (1984). MSC: 47-06 00A27 47B37 47B10 47B35 47A65 41A30 46M20 PDFBibTeX XMLCite J. Sov. Math. 26, 2137--2169 (1984; Zbl 0543.47001) Full Text: DOI
Vershik, A. M.; Malozemov, V. N.; Pevnyi, A. B. Best piecewise polynomial approximation. (English) Zbl 0333.41006 Sib. Math. J. 16(1975), 706-717 (1976). MSC: 41A10 41A50 41A15 PDFBibTeX XMLCite \textit{A. M. Vershik} et al., Sib. Math. J. 16, 706--717 (1976; Zbl 0333.41006) Full Text: DOI
Vershik, A. M.; Malozemov, V. N.; Pevnyi, A. B. Best piecewise polynomial approximation. (Russian) Zbl 0328.41006 Sib. Mat. Zh. 16, 925-938 (1975). MSC: 41A10 41A50 41A15 PDFBibTeX XMLCite \textit{A. M. Vershik} et al., Sib. Mat. Zh. 16, 925--938 (1975; Zbl 0328.41006)