Leeches as Sensor-bioindicators of River Contamination by PCBs oleh Gorzyslaw Poleszczuk, Jana Hajslova, Jana Pulkrabova, Zdenka Svobodova, Josef Velisek, Tomas Randak, Jana Machova, Blanka Vykusova, Vladimir Zlabek, Jitka Kolarova, Stanislava Macova, Danka Harustiakova