Printed
Urban Lichens (1) on Trees and Wood by Frank Dobson (Field Studies Council, Wild ID fold-out card, 2006)
Urban Lichens (2) on Stone and Soil by Frank Dobson (Field Studies Council, Wild ID fold-out card, 2006)
Common Churchyard Lichens by Frank Dobson (Field Studies Council, Wild ID fold-out card, 2004)
Lichens on Twigs by Wolseley, James & Alexander (Field Studies Council, Wild ID fold-out card, 2003)
Lichens: an Illustrated Guide to the British and Irish Species by Frank Dobson (2018 7th edition). Richmond Publishing and British Lichen Society. 496 pages.
Websites
Google Lens: Go to google.com and there is a camera icon at the right of the search bar. Click on this, and you can drag and drop any image and it will do its best to identify it – so can be used for any flora and fauna, vertebrates and invertebrates etc. (as well as buildings, landscapes – anything, in fact.) Worth a look, but treat identifications with caution!
Apps