Literature shows that there are two main reasons to apply clustering for paraphrase extraction. On one hand, as<cite> (Barzilay & Lee, 2003)</cite> evidence, clusters of paraphrases can lead to better learning of text-totext rewriting rules compared to just pairs of paraphrases. On the other hand, clustering algorithms may lead to better performance than stand-alone similarity measures as they may take advantage of the different structures of sentences in the cluster to detect a new similar sentence.