1. Yu. M. Berezanskii, ?On decomposition into eigenfunctions of self-adjoint operators,? Ukr. Mat. Zh.,11, No. 1, 16?24 (1959).
2. F. A. Berezin and M. A. Shubin, Schrödinger Equation [in Russian], Nauka, Moscow (1983).
3. C. Foias, ?Decompositions integrales des families spectrales et semispectrales en operateurs qui sortent de l'espace hilbertien,? Acta Sci. Math.,20, Nos. 2?3, 117?155 (1959).
4. Yu. M. Berezanskii, Decomposition into Eigenfunctions of Self-Adjoint Operators [in Russian], Naukova Dumka, Kiev (1965).
5. M. Reed and B. Simon, Methods of Contemporary Mathematical Physics [Russian translation], Mir, Moscow (1977).