Hawksworth, D.L., 1983
A Key to the Lichen-forming, Parasitic, Parasymbiotic and Saprophytic Fungi occurring on Lichens in the British Isles
Reprinted from Lichenologist 15(1): 1-44, single-sided printing, so alternate pages are blank. A useful guide, but now (2004) rather outdated by the discovery of as many species again.
A useful review in British Wildlife (vol 15, No 3, Feb 2004, pp 192-199) gives an overview of more recent developments.
||The British Lichen Society (BLS)
||All the British species then known.
||Two pages of line and stipple drawings at the back.
||Under a Compound Microscope.
||Microscope slides of spores/asci usually needed; staining with Melzer's Iodine for asci.
||Comparatively straightforward, if the lichen is identified.