@patent {4,
	title = {Zirconia Toughening of Glass-Ceramic Materials},
	volume = {5045402},
	year = {1991},
	edition = {United States of America},
	chapter = {US},
	url = {/files/clarke/files/us5045402.pdf},
	author = {Adams, Richard W. Jr. and David R. Clarke and Sara H. Knickerbocker and Linda L. Rapp and Bernard Schwartz}
}
