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I can help you only with twitter:

https://twitter.com/search?q=""http://moz.com""&src=typd

Just replace the http://moz.com with your domain.

For Facebook or Linkedin I don't think you can do that, but you can find people who liked your Facebook page or who shared your Facebook posts.

To avoid duplicate content you need to use the rel=”alternate” href=”x” tag. You dont have to buy a domain, here are several ways you can organise your website.

ccTLDs - [example.ie]

Pros

• Clear geotargeting
• Server location irrelevant
• Easy separation of sites

Cons

• Expensive (and may have limited availability)
• Requires more infrastructure
• Strict ccTLD requirements (sometimes)

****Subdomains with gTLDS [de.example.com]

Pros

• Easy to set up
• Can use Webmaster Tools geotargeting
• Allows different server locations
• Easy separation of sites

Cons

• Users might not recognize geotargeting from the URL alone (is “de” the language or country?)

Subdirectories with gTLDs [example.com/de/]

Pros

• Easy to set up
• Can use Webmaster Tools geotargeting
• Low maintenance (same host)

Cons

• Users might not recognize geotargeting from the URL alone
• Single server location
• Separation of sites harder

URL parameters [site.com?loc=de]

Pros

• Not recommended.

Cons

• URL-based segmentation difficult
• Users might not recognize geotargeting from the URL alone
• Geotargeting in Webmaster Tools is not possible

You can have even the same content for example, if you have a version for the UK and another for the US the content will be very similar.

Hope this helps

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