@article {beale2007accuracy,
	title = {On the accuracy of finite difference methods for elliptic problems with interfaces},
	journal = {Communications in Applied Mathematics and Computational Science},
	volume = {1},
	number = {1},
	year = {2007},
	pages = {91{\textendash}119},
	publisher = {Mathematical Sciences Publishers},
	author = {Beale, Thomas and Layton, Anita}
}