Using new technology algrithm, google allow each person to make a duplicate content in access using multiple URLs. Duplicate content still considered by Google for access by Googlebot and the index by the search engine Google.
Duplicate URL that has this content must follow the Google webmaster rules that have been provided by Google. Google understands that in order to duplicate the URL under control and you want the index by Googlebot then you have to use tags rel="canonical"
Sample URLs that use duplicate content:
By using the rel = "canonical", all URLs that have duplicate content will be in the index by the search engine Google.