We have multilingual websites with some content variations but 60% of the content on site remains the same. We have used rel=alternate hreflang on corresponding ccTLDs respective countries. for example on example.com we have used <link rel="alternate" hreflang="ja" href="http://www.example.co.jp/" /> <link rel="alternate" hreflang="en-GB" href="http://www.example.co.uk/" /> <link rel="alternate" hreflang="de" href="http://www.example.de/" /> Now should we also use link rel="canonical" href="example.com" on all ccTLDs? What are the advantages and disadvantage of using it?