2 citations to https://www.mathnet.ru/eng/dan39266

1. P. D. Lamberti, V. Vespri, “Remarks on Sobolev–Morrey–Campanato spaces defined on $C^{0,\gamma}$ domains”, Eurasian Math. J., 10:4 (2019), 47–62    
2. V. I. Burenkov, A. L. Gorbunov, “Exact bounds for the minimum norm of extension operators for Sobolev spaces”, Izv. Math., 61:1 (1997), 1–43