1. S. Albeverio, F. Gesztesy, R. Hoegh-Krohn, and H. Holden, ?Solvable models in quantum mechanics?, Springer-Verlag, 1988.
2. S. Albeverio, W. Karwowski, and V. Koshmanenko, Square powers of singularly perturbed operators, Math. Nachr.173 (1995) 5?24.
3. S. Albeverio and P. Kurasov, Rank one perturbations, approximations and selfadjoint extensions, Preprint SFB 237 Nr 304.
4. S. Albeverio and V. Koshmanenko, Kiev Preprint, 1996.
5. S. Benvegnu and L. Dabrowski, ?Relativistic Point Interaction in One Dimension?, Preprint SISSA 4/95/FM.