1. J. Avron, I. Herbst, B. Simon, Schrödinger operators with magnetic fields. I. General interactions, Duke Math. J. 45 (1978), 847–883.
2. J. Avron, R. Seiler, B. Simon, The index of a pair of projections, J. Funct. Anal. 120 (1994), 220–237.
3. F.A. Berezin, M.A. Shubin, The Schrödinger Equation. Kluwer Academic Publishers, Dordrecht, 1991.
4. M.Ŝ. Birman, M.G. KreÎn, On the theory of wave operators and scattering operators, Dokl. Akad. Nauk SSSR 144 (1962), 475–478 (Russian); English translation in Soviet Math. Doklady 3 (1962).
5. M.Ŝ. Birman, D.R. Yafaev, The spectral shift function. The papers of M. G.KreÎn and their further development, Algebra i Analiz 4 (1992), 1–44 (Russian); English translation in St. Petersburg Math. J. 4 (1993), 833–870.