-An online plagiarism detection can be viewed as a reverse engineering task where \r
-we need to find original documents from which the plagiarized document was created.\r
-During the process the plagiarist locates original documents with the use of a search engine.\r
-The user decides what query the search engine to ask and which of the results from the result page to use.\r
-In the real-world scenario the corpus is the whole Web and the search engine can be a contemporary commercial search engine\r
-which scales to the size of the Web. This methodology is based on the fact that we do not\r
-possess enough resources to download and effectively process the whole corpus.\r
-In the case of PAN 2013 competition the corpus\r
-of source documents is the ClueWeb\footnote{\url{http://lemurproject.org/clueweb09.php/}} corpus.\r
-\r
-As a document retrieval tool for the competition we utilized the ChatNoir~\cite{chatnoir} search engine which indexes the English\r
-subset of the ClueWeb. \r