Chapman, J.L. and M.J.Reiss (1992) Ecology – principles and applications, Cambridge University Press

Tudge,C (1991) Global ecology, Oxford University Press

UK Government (1994), Biodiversity - The UK action plan, HMSO

Wheater, P.C (1999) Urban habitats, Routledge Press

Wilson, E.O (editor) (1990) Biodiversity, National Academy Press, USA