RG Novikov - Funktsional'nyi Analiz i ego Prilozheniya, 1988 - mathnet.ru
RG Novikov, “Multidimensional inverse spectral problem for the equation $-\Delta\psi+(v(x)-Eu(x))\psi=0$”,
Funktsional. Anal. i Prilozhen., 22:4 (1988), 11–22; Funct. Anal. Appl., 22:4 (1988), 263–272 …