1. M. Sh. Birman and M. Z. Solomyak, ?Double Stieltjes operator integrals,? Problemy Mat. Fiz., No. 1, 33?67 (1966).
2. M. Sh. Birman and M. Z. Solomyak, ?Double Stieltjes operator integrals. II,? Problemy Mat. Fiz., No. 2, 26?60 (1967).
3. M. Sh. Birman and M. Z. Solomyak, ?Double Stieltjes operator integrals. III,? Problemy Mat. Fiz., No. 6, 27?53 (1973).
4. V. V. Peller, ?Hankel operators in the perturbation theory of unitary and self-adjoint operators,? Funkts. Anal. Prilozhen.,19, No. 2, 37?51 (1985).
5. M. G. Krein, ?On some new studies in the perturbation theory of self-adjoint operators,? in" First Mathematics Summer School, Part I [in Russian], Naukova Dumka, Kiev (1964), pp. 103?184.