2 citations to https://www.mathnet.ru/rus/mzm10978

1. H. A. Matevossian, “Biharmonic Problem with Steklov-type Conditions on the Boundary of the Domain”, Lobachevskii J Math, 45:12 (2024), 6552  
2. Chichoyan S.F., “Smoothness of solutions of the Dirichlet problem for the biharmonic equation in nonsmooth 2D domains”, Differ. Equ., 52:2 (2016), 260–264