+Due to the increasing ease of plagiarism the plagiarism detection has nowadays become a need for many institutions.
+Especially for universities where modern learning methods include e-learning and a vast document sources are online available.
+%In the Information System of Masaryk University~\cite{ismu} there is also an antiplagiarism tool which is based upon the same principles as are shown in this paper.
+The core methods for automatic plagiarism detection, which also work in practice on extensive collections of documents,
+are based on computation document similarities. In order to compute a similarity
+we need to possess the original and the plagiarized document.
+%The most straightforward method is to use an online search engine in order to enrich
+%document base with potential plagiarized documents and evaluate the amount of plagiarism by detailed document comparison.
+%In this paper we introduce a method which has been used in PAN 2012 competition\footnote{\url{http://pan.webis.de/}}
+%in plagiarism detection.