Nikol’skij, S. M. Sur les theoremes d’immersion, prolongement et approximation des fonctions derivables des plusieurs variables. (Romanian) Zbl 0269.26011 Acad. Republ. popul. Romine, Fil. Cluj, Inst. Calcul, Studii Cerc. Mat. 12, 97-143 (1961). Page: −5 −4 −3 −2 −1 ±0 +1 +2 +3 +4 +5 Show Scanned Page Cited in 1 Document MSC: 26B05 Continuity and differentiation questions 41A65 Abstract approximation theory (approximation in normed linear spaces and other abstract spaces) 41A30 Approximation by other special function classes 46E35 Sobolev spaces and other spaces of “smooth” functions, embedding theorems, trace theorems PDF BibTeX XML Cite \textit{S. M. Nikol'skij}, Acad. Repub. Popul. Romine, Fil. Cluj, Inst. Calcul, Studii Cerc. Mat. 12, 97--143 (1961; Zbl 0269.26011)