Bick, H. (1972). Ciliated protozoa: An illustrated guide to the species used as biological indicators in freshwater biology. World Health Organization.
Chicago-viite (17. p.)Bick, Hartmut. Ciliated Protozoa: An Illustrated Guide to the Species Used as Biological Indicators in Freshwater Biology. Geneva: World Health Organization, 1972.
MLA-viite (9. p.)Bick, Hartmut. Ciliated Protozoa: An Illustrated Guide to the Species Used as Biological Indicators in Freshwater Biology. World Health Organization, 1972.
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