2 citations to https://www.mathnet.ru/rus/de10212

1. Anton Savin, “The Friedrichs Extension of Elliptic Operators with Conditions on Submanifolds of Arbitrary Dimension”, Mathematics, 12:3 (2024), 418  
2. A. Yu. Savin, E. N. Semenova, “A Spectral Sobolev Problem for the Biharmonic Operator”, Lobachevskii J Math, 44:3 (2023), 950