Galya Kapanen and  Jaan–Mati Punning and  Irina Blinova and  Külli Kangur,  The Roles of Natural and Anthropogenic Factors of Ecological State in the Lake Peipsi .   journal   = {International Journal of Environmental and Ecological Engineering}, [online]. World Academy of Science, Engineering and Technology.
    April 2007, vol. 4(4). 12 - 17
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