On typology and reference conditions for phytoplankton in rivers and lakes in Germany
  Ute Mischke; Brigitte Nixdorf; Horst Behrendt
            2002
      
  Typology and ecological classification of lakes and rivers / Marja Ruoppa ; Krister Karttunen (eds.). - Kobenhavn, 2002 - (TemaNord ; 2002, 566), S. 44-49