M. Sh. Birman, M. Z. Solomyak, “Estimates of singular numbers of integral operators”, Russian Math. Surveys, 32:1 (1977), 15–89
G. P. Kostometov, “Asymptotic behavior of the spectrum of integral operators with a singularity on the diagonal”, Math. USSR-Sb., 23:3 (1974), 417–424
B. V. Pal'tsev, “Expansion in eigenfunctions of integral operators of convolution on a finite interval with kernels whose Fourier transforms are rational. “Weakly” nonselfadjoint regular kernels”, Math. USSR-Izv., 6:3 (1972), 587–630
M. Sh. Birman, M. Z. Solomyak, “Leading term in the asymptotic spectral formula for “nonsmooth” elliptic problems”, Funct. Anal. Appl., 4:4 (1970), 265–275