1. European Commission , Official Journal of the European Communities, 2000, p. 77
2. J. Illies , Limnofauna Europaea, G. Fischer Verlag, Stuttgart, 1978
3. M. Wallin , T.Wiederholm and R. K.Johnson, Guidance on establishing reference conditions and ecological status class boundaries for inland surface waters, Produced by CIS Working Group 2.3 –REFCOND, 2003
4. WFD CIS Guidance Document No. 10 , Rivers and lakes - Typology, reference condition and classification systems, Produced by Working Group 2.3 -REFCOND, 2003
5. Nutrient pressures and ecological responses to nutrient loading reductions in Danish streams, lakes and coastal waters