@inbook {1712,
	title = {Lichen sensitivity to air pollution},
	booktitle = {Lichen Biology},
	year = {2008},
	publisher = {Cambridge University Press},
	organization = {Cambridge University Press},
	edition = {2nd edition},
	chapter = {13},
	address = {Cambridge},
	author = {Gries, C.}
}
@article {695,
	title = {Lichens as bioindicators of sulfur dioxide},
	volume = {33(1)},
	year = {2002},
	pages = {1-21},
	author = {Nash, T.H. and Gries, C.}
}
