If an Indiegogo link, such as this one, gets shared on G+, their G+ page is displayed in the post in the place where commonly the URL would be displayed.
I've tried looking analyzing the HTML, but came up empty handed: there's Twitter cards metadata, there's OpenGraph, there is a G+ button -- but I found nothing that links to Indiegogo's page, not even rel="publisher"
.
So, how does Indiegogo achieve this?