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2. M. E. Hale, The Biology of Lichens, (Edward Arnold, London,1983, 3rd edn), pp. 190.
3. K. J. Puckett, Lichens, Bryophytes and Air Quality, (Bibl. Lichenol., J. Cramer, Berlin, 1988), 30, pp. 231–267.
4. Analysis of Heavy Metals Concentration in Soil and Litchens from Various Localities of Hosur Road, Bangalore, India
5. Abida Begum, S. Harikrishna K. Veena and Irfanulla Khan, Lichens are indicators of Heavy metal pollution, Pollution News, 4, (2008).