@article {2003,
	title = {Singularly perturbed elliptic equations with symmetry: existence of solutions concentrating on spheres, Part I},
	journal = {Comm. Math. Phys. 235 (2003) no.3, 427-466},
	number = {SISSA;63/2002/M},
	year = {2003},
	publisher = {Springer},
	doi = {10.1007/s00220-003-0811-y},
	url = {http://hdl.handle.net/1963/1633},
	author = {Antonio Ambrosetti and Andrea Malchiodi and Wei-Ming Ni}
}
