I got your point, it due to the content of article only. In Joomla, an article will have intro text and full text and a 'readmore' button will separate these 2 content parts.
However, these articles on your site don't have them so it will consider the fulltext as introtext and show them all. That's why you see duplicated content.
I just edited this article: Classifiche by adding a readmore button on top of content and it's showing correctly now:
http://www.ceresini.it/index.php/classifiche
You can apply the same for other articles.