@book {676, title = {Biology of Freshwater Pollution}, year = {1996}, publisher = {Longman}, organization = {Longman}, address = {Harlow}, author = {Mason, C.F.} } @article {675, title = {Acidification and Otter (Lutra-Lutra) Distribution in Scotland}, journal = {Water, Air and Soil Pollution}, volume = {43}, year = {1989}, pages = {365-374}, author = {Mason, C.F. and Macdonald, S.M.} } @article {677, title = {Acidification and otter Lutra lutra distribution on a British river. }, volume = {51}, year = {1987}, pages = {81-87}, author = {Mason, C.F. and Macdonald, S.M.} }