@inbook {Shepard1968ACM,
	title = {{A two-dimensional interpolation function for irregularly-spaced data}},
	booktitle = {Proceedings of the 1968 ACM National Conference},
	year = {1968},
	pages = {517-524},
	publisher = {ACM Press},
	organization = {ACM Press},
	address = {New York},
	author = {Shepard, D.},
	editor = {Blue, R.~B.~Sr. and Rosenberg, A.~M.}
}