River water quality : ecological assessment and control / Commission of the European Communities. Directorate-General Environment, Nuclear Security, Civil Protection. —  Luxembourg : Office for Official Publications of the European Communities, 1992. —  CIDIMA. —  751 p. : il., gráf., tab. ; 30 cm. — 
    ISBN 92-826-2929-5
   1. Ríos.2. Calidad del agua. I. Comisión Europea.
504.453