1. M. Abramowitz and I.A. Stegun, Handbook of Mathematical Functions with Formulas, Graphs, and Mathematical Tables, National Bureau of Standards Applied Mathematics Series, Vol. 55, U.S. Government Printing Office, Washington, D.C., 1964, for sale by the Superintendent of Documents.
2. Point interactions in two dimensions: Basic properties, approximations and applications to solid state physics;Albeverio;J. Reine Angew. Math.,1987
3. S. Albeverio, F. Gesztesy, R. Høegh-Krohn and H. Holden, Solvable Models in Quantum Mechanics, 2nd edn, AMS Chelsea Publishing, Providence, RI, 2005, with an Appendix by Pavel Exner.
4. On point interactions in one dimension;Albeverio;J. Operator Theory,1984
5. H. Ammari, H. Kang and H. Lee, Layer Potential Techniques in Spectral Analysis, Mathematical Surveys and Monographs, Vol. 153, American Mathematical Society, Providence, RI, 2009.