https://moz.com/community/q/topic/19595/could-you-use-a-robots-txt-file-to-disalow-a-duplicate-content-page-from-being-crawled/11
Could you use a robots.txt file to disalow a duplicate content page from being crawled? | SEO Forum...
Jun 4, 2012 - Yeah, sorry for the confusion. I put the tag on all the pages (Original and Duplicate). I sent you a PM with another good article on Rel canonical tag