1. H. Baumgärtel, H. Kaldass and S. Komy: On spectral properties of
resonances for selected potential
scattering systems, J. Math. Phys. 50, 023511 (2009);
2. M. Reed and B. Simon: Methods of Modern Mathematical
Physics III: Scattering Theory, Academic, New York 1978.
3. H. Baumgärtel: Generalized Eigenvectors for Resonances
in the Friedrichs Model
and Their Associated Gamov
Vectors, Rev. Math. Phys. 18, 61–78 (2006).
4. H. Baumgärtel: Spectral and Scattering Theory
of Friedrichs Models on
the Positive Half Line
with Hilbert-Schmidt Perturbations, Annales Henri Poincare’ 10, 123–143 (2009).
5. A. Bohm and M. Gadella: Dirac Kets, Gamov Vectors
and Gelfand Triplets, Lecture Notes in Physics, Vol. 348 (Springer-Verlag Berlin 1989); O. Civitarese, M. Gadella, Physical and Mathematical aspects
of Gamow states, Physics Reports, 396, 41–113 (2004).