• Classif[i]cation of chemical status of riversLoigu, Enn; Leisk, Ülle"Environmental Impact and Water Management in a Catchment Area Perspective" : 24-26 September, 2001, Tallinn, Estonia : proceedings of the Symposium dedicated to the 40th Anniversary of Institute of Environmental Engineering at Tallinn Technical University2001 / p. 46-53 : ill