@article {Guo:March 1996:0925-4005:139,
	author = "Guo X.",
	author = "Sun Y.-Q.",
	author = "Cui K.",
	title = "Darkening of zirconia: A problem arising from oxygen sensors in practice",
	journal = "Sensors and Actuators B: Chemical",
	volume = "31",
	year = "March 1996",
	abstract = "",
	pages = "139-145(7)",
	url = "http://www.ingentaconnect.com/content/els/09254005/1996/00000031/00000003/art80058"
	doi = "doi:10.1016/0925-4005(96)80058-X"
}