Duplicate pages without canonical Description & How to Fix
Pages with duplicate or very similar content that don't specify their canonical version.
Although Google asserts that they can automatically choose the best version of the content to show in their search results, it won't necessarily be page version you want to be indexed. That is why similar or duplicate pages of your website must have a "rel=canonical" attribute to instruct search engines to show the most authoritative (canonical) version of the page in search results.
How to fix
For every page in the group of duplicates, you should pick one canonical version that you want to be indexed in search results. Add its URL to the "rel=canonical" labeling on each page with duplicated content, including the canonical page itself.