TY - JOUR T1 - Quadratic forms for singular perturbations of the Laplacian JF - Publ. Res. Inst. Math. Sci. 26 (1990), no. 5, 803--817 Y1 - 1990 A1 - Alessandro Teta PB - SISSA Library UR - http://hdl.handle.net/1963/757 U1 - 3034 U2 - Mathematics U3 - Mathematical Physics ER -