Reference sources for lichen identification, descriptions, habitat details and synonyms include:
The Lichens of Great Britain and Ireland - edited by Smith et.al, 2009
The Lichen Flora of Great Britain and Ireland - edited by O. W. Purvis, 1992
Lichens An Illustrated Guide to the British and Irish Species - Frank Dobson, 2005
Lichens of North America - Brodo, Sharnoff & Sharnoff, 2001
The Macrolichens of New England - Hinds & Hinds, 2007
WEBLINKS:
The British Lichen Society: Publications
LichenIreland: References
Summerfield Books: Ferns, Mosses and Lichens
NHBS Bookstore: Lichens
LICHEN SYNONYMS:
British Lichen Society: Synonyms
Lichens of Ireland Project: Synonyms