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Starting on the 14 May 2014, severe rainfall hit south-eastern Europe. The recent period had already been wet and the ground was more or less saturates. On 18 May, the Bosnia and Herzegovina and Serbia requested assistance through the EU Civil Protection Mechanism. Serbia declared a state of emergency on Thur 15 May.
http://www.reuters.com/article/2014/05/15/us-balkans-flood-idUSBREA4E0PA20140515
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