Keyword "LICHEN" in:

Fast-formed case hardened surfaces on exposures of Hrubá Skála sandstone: microscopic, tensile strength, erodability, origin, and significance for sandstone landscape
Schweigstillová,J., Bruthans,J., Falteisek,L., Válek,J., Soukup,J., volume 46, 2013 (GRR for 2012), pages 228–234
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