@article {1991,
	title = {Shape optimization for Dirichlet problems: relaxed formulations and optimally conditions},
	journal = {Appl.Math.Optim. 23 (1991), no.1, p. 17-49.},
	number = {SISSA;124/89/M},
	year = {1991},
	publisher = {SISSA Library},
	url = {http://hdl.handle.net/1963/880},
	author = {Giuseppe Buttazzo and Gianni Dal Maso}
}
