@article {606,
	title = {Lichen Recolonization in London under Conditions of Rapidly Falling Sulfur-Dioxide Levels, and the Concept of Zone Skipping.},
	journal = {Botanical Journal of the Linnean Society},
	volume = {100},
	year = {1989},
	pages = {99-109},
	author = {Hawksworth, D.L. and McManus, P.M.}
}
