Dyfyniad APA

 Hellawell, J. M. (1986).  Biological indicators of freshwater pollution and environmental management.  Elsevier Applied Science Publishers.

Dyfyniad Arddull Chicago

 Hellawell, J. M.  Biological Indicators of Freshwater Pollution and Environmental Management.  Elsevier Applied Science Publishers, 1986.

Dyfyniad MLA

 Hellawell, J. M.  Biological Indicators of Freshwater Pollution and Environmental Management.  Elsevier Applied Science Publishers, 1986.

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