Possibly canonical links. HN looks at the submissions and updates the links to the canonical link if present. I'm on mobile so not able to double check the Goog

Possibly canonical links. HN looks at the submissions and updates the links to the canonical link if present. I'm on mobile so not able to double check the Google books page at the moment, but if you view source check to see if there's a canonical link in there. This also bites some blogging sites that end up with a canonical link to their base http://blog.example.com http://blog.example.com on all their posts. https://en.wikipedia.org/wiki/Canonical_link_element https://en.wikipedia.org/wiki/Canonical_link_element