@article {1990,
	title = {Quadratic forms for singular perturbations of the Laplacian},
	journal = {Publ. Res. Inst. Math. Sci. 26 (1990), no. 5, 803--817},
	number = {SISSA;165/88/FM},
	year = {1990},
	publisher = {SISSA Library},
	url = {http://hdl.handle.net/1963/757},
	author = {Alessandro Teta}
}
