Lecanora chlarotera Nyl.
Common on smooth, nutrient-rich barked trees. The commonest of a complex of similar species that require chemical tests and microscopic examination for certain identification
Smith, C.W. et al. editors (2009) The Lichens of Great Britain and Irelandd
Dobson, F.S. (2018) Lichens: an Illustrated Guide to the British and Irish Species