@inbook {28961,
	title = {The preconditioned conjugate gradient method for solving elliptic difference equations},
	booktitle = {Numerical Approximation of Partial Differential Equations},
	year = {1987},
	pages = {205-217},
	publisher = {Elsevier Sci. Pub. North-Holland},
	organization = {Elsevier Sci. Pub. North-Holland},
	edition = {EL Ortiz, Editor},
	author = {I. C. Demetriou and DJ Evans}
}
