@book{25740,
	author = {Ribbing, Carl, ed.},
	title = {Hard Materials in Optics},
	publisher = {SPIE},
	year = {1990},
	series = {Proceedings of SPIE; V. 1275},
	address = {Washington, USA},
	url = {https://www.spiedigitallibrary.org/conference-proceedings-of-spie/1275}
}